I'm a computer science student, so assume me with required ability.
Also I've searched this issue for a whole afternoon, I'll list the methods that I tried below.
Environment:
M8 android 6.0, s-off, unlocked bootloader, rooted, twrp recovery
Some modification to system partition(hosts, busybox, bloatware removed)
Set-up before applying an small ota(~89mb):
Since it's a trivial update, I didn't bother reflash all the system image - and I can't find one for my country(TW)either.
I documented every change in system partition, so I did the following steps to prepare.
1. removed xposed framework
2. unrooted by supersu built-in function.
3. put deleted bloatware back to /system/app, /system/priv-app .
libRSSupport.so and librsjni.so under /system/lib/ have been modified and I don't know why - whatever, I replaced them with the stock one.
4. reflashed stock recovery
I DID NOT(forgot to) uninstall busybox and revert the changes of hosts file, if this matters.
/system/bin/app_process32, boot partion and Supersu modified files are "likely" to be restored to stock.(I have no way to confirm.)
Problem:
Applied OTA, it rebooted to a green spinning circle with progression bar- regular OTA procedure.
But, it stuck at 25% for seconds(guess it's system partition integrity check), and progressed to 53%, stuck at 53% for about 10s.
And then it rebooted, entered OTA update mode again, and so on. I STUCKED AT OTA LOOP.
Methods that I've tried:
Pressed pwr+up under light for 10+ seconds - phone won't accept power button input during OTAs.
Pressed pwr+down / down only when reboot - can't enter fastboot, still OTA updating.
Connected to PC - adb devices not found, fastboot reboot recovery no response.
The current method that I figured out:
I'd like to wait until it drained out, check if charging it shows the normal charging mini kernel.
If so, try button combination into fastboot.
Guess if xda can't help, I'll have to ask for htc... : (
Unrooting the ROM doesn't work; you need full stock ROM to OTA.
But having a non-stock (unrooted) ROM will usually result in an error, and no OTA installation. So I agree this is a big weird.
29988122 said:
Pressed pwr+up under light for 10+ seconds - phone won't accept power button input during OTAs.
Click to expand...
Click to collapse
Try holding power + vol up for 30 seconds or more; even up to a minute (if there is no change). I'm not sure if updating OTA will impact this, but that button combo will force a reboot in every other situation I've seen when the screen is on.
Quick followup:
After battery depleted and complete shut off, I tried reboot to fastboot(by pushing power+down / down only)
No avail.
Even by charging only, it would immediately enter OTA.
I guess htc's OTA would write itself into bootloader, and thus I WON'T be able to enter the normal bootloader/recovery until OTA's completed.
But in my case, OTA's got error so....I got stuck at OTA loop!
The encryption key of my sdcard(adopted storage) was still inside phone's data partition....
Do I really need to give up?
: ( ....
29988122 said:
I guess htc's OTA would write itself into bootloader, and thus I WON'T be able to enter the normal bootloader/recovery until OTA's completed.
Click to expand...
Click to collapse
What is happening, is that the bootloader is designed to automatically look for an update file and install it, before it gives you the other bootloader options.
I've seen another with the similar problem. I couldn't think of anything in that case either. You really can't do much if you can't get to fastboot or delete the OTA file (and I can't think of any way you would do either of those, that hasn't already been tried).
What happens if you remove the SD card? Does it still try to install OTA?
redpoint73 said:
What is happening, is that the bootloader is designed to automatically look for an update file and install it, before it gives you the other bootloader options.
I've seen another with the similar problem. I couldn't think of anything in that case either. You really can't do much if you can't get to fastboot or delete the OTA file (and I can't think of any way you would do either of those, that hasn't already been tried).
What happens if you remove the SD card? Does it still try to install OTA?
Click to expand...
Click to collapse
Ya, still installing OTA.
Someone has told me a way to bypass OTA, somehow it worked. I'll post it here in case someone faced the same situation as I did.
1. let it do the OTA loop until power automatically shut down.
2. take out both sim and sdcard.
3. MANUALLY boot, let it auto shut down, repeat until it can only boot for few seconds or less.
4. plug in charger, check if charging mini kernel appeared or not. If not, repeat step 3.
5. it is told that the bootloader has some kind of low battery protection mechanism that it would skip OTA's under extremely low battery condition. Therefore after 30s or a little bit more charging, pull the plug(essentially shut it down), then magically you can now boot into bootloader via pwr+down.
Of course you'll wanna charge until about 30% or more, then reflash twrp and system partition... : p
Thank you xda and redpoint73, you just made my day!
Related
hi guys,
today i made a huge mistake. i was trying to deinstall the cm9 by just wiping my phone. accidentaly i made a "system wipe" with my recovery. now my phone ist stuck in the "this build is for development purposes only" screen. i tried to reboot into recovery via the aio kit - error: device not found. (led not flashing, not even when i connect it to the "normal" loading adapter). i just read another thread which ended in sending the device back to htc. i wonder if there is any possibility to safe my phone from that.
greetz bow111
Are you able to acces the Bootloader by closing the phone and restart it by keeping pressed at same time VOLUME DOWN + POWER ?
Be careful: Do NOT press volume UP!, Do not hold Volume Down for too long!
Once you are in the bootloader you should be able to:
A:Go into recovery and repair it from there in you have the ROM on your SD card.
B:If you are unable to acces recovery mode from bootloader, try to use the All In One Tool and flash the TWRP Recovery (the one in the right part of the window) also, note that there are too version, CDMA and GSM, if you have a sim card flash GSM, if you do not have a simcard use CDMA.
Let me know how it went
rzarectha said:
Are you able to acces the Bootloader by closing the phone and restart it by keeping pressed at same time VOLUME DOWN + POWER ?
Be careful: Do NOT press volume UP!, Do not hold Volume Down for too long!
Once you are in the bootloader you should be able to:
A:Go into recovery and repair it from there in you have the ROM on your SD card.
B:If you are unable to acces recovery mode from bootloader, try to use the All In One Tool and flash the TWRP Recovery (the one in the right part of the window) also, note that there are too version, CDMA and GSM, if you have a sim card flash GSM, if you do not have a simcard use CDMA.
Let me know how it went
Click to expand...
Click to collapse
ok. my phone just quick restarted. it directly went back to the "htc quietly brilliant" screen. pressing volume down + power button for a few seconds doesnt work to get into bootloader. i tried it serveral times. im not even able to turn the phone off. holding the power button only wont help at all.
thanks for ur help.
edit: i feel.. pranked now it worked and i went from bootloader to recovery (twrp already installed). can u tell me what to do now? thanks a lot already
Hm,
Well since you cant remove the battery on this phone, id suggest to just let it finish with what it has left off of the battery. once it is closed try to recharge it and then try to boot in recovery, ofc you might not be able to do this today, depends how much battery you had left when the problem started, but it's a chance, also if it's rooted you bootloader will be unlocked so i doubt HTC will grant you warranty for it (not 100% about this though). let us know if you manage to do any progress with it after you manage to make it close.
cheers
rzarectha said:
Hm,
Well since you cant remove the battery on this phone, id suggest to just let it finish with what it has left off of the battery. once it is closed try to recharge it and then try to boot in recovery, ofc you might not be able to do this today, depends how much battery you had left when the problem started, but it's a chance, also if it's rooted you bootloader will be unlocked so i doubt HTC will grant you warranty for it (not 100% about this though). let us know if you manage to do any progress with it after you manage to make it close.
cheers
Click to expand...
Click to collapse
i just edited my post. managed to get into recovery (twrp). what do i have to do now?
Download a new rom and transfer it to your sd card, then flash it from your recovery.
If u have the ROM in the SD card just flash it and reboot other wise as he mentioned above
Sent from my One V using xda premium
Ok, last night i went to sleep.
You now need to find a way to put a ROM on your SD card. whatever ROM you choose make sure you have the correct kernel for it (in every post for ROMs you will find a download link to the correct kernel aswell).
So what you do now (after you have the ROM .zip file on your SD card and your Kernel file in your PC) is:
-Put your phone into Bootloader, Select fast boot and connect the USB cable, and make sure it tells on your phone "FASTBOOT USB"
-Then in All in One select "Flash Kernel" and browse to the correct Kernel, and flash it.
-Reboot your phone in Recovery mode, you have the option in the fastboot screen.
-In the Recovery menu select Factory Reset -> Wipe System.
-While still in recovery go to "Install update from SD card" (or something similar) and choose the ROM .zip file, wait for it to be flashed
-reboot your phone (1st boot is always a bit slower, could take up to 5 minutes).
-after you get to your main screen, reboot the phone again and flash a Google Apps (gapps) .zip file. You will find the correct version from your ROM in the official thread of the ROM. You DO NOT run a factory reset, wipe system or anything like that for flashing Gapps.
Good luck.
got my phone working again. additionally i tried to "re-stock" my phone via a ruu.exe. now i have a new problem ( -.- ;D). my phone wont connect to wlan. it always hangs on "authenticating with wifi (dont know if translated it the right way)". some has an idea how to solve that problem?
p.s. sry for answering this late. had to do a lot of stuff for my finals :/
edit: was a problem with my router
flash a proper kernel
Sent from my One V
After a update for better compatibility for 3rd party app, my Zenfone wont get past the ASUS screen at all.
Im also stuck at the asus load screen. I played around with the permissions of the sd card, after rebooting its stuck. Guys how to unbrick?
bratski said:
Im also stuck at the asus load screen. I played around with the permissions of the sd card, after rebooting its stuck. Guys how to unbrick?
Click to expand...
Click to collapse
you may want to flash your phone back. so this consist of
1) read up how to access to Temp CWM
2) download and transfer the full rom to your SD card
3) do a wipe all partition and go to advanced setting, wipe cache
4) install zip and choose from external SD, point to that .zip file for the full rom and apply.
5) installation may take 10min or so do not switch it off. after installation you are good as new.
I believe this should solve your problem, normal if things get bricked is due to config file error could be [syntax, corrupted, missing, setting].
Flashing should solve mostly of it unless the file that you previously accessed require root and cwm does not give permission to the file. that is a permanent bricking.
As always, newbie should not try tweaking permission required files, you end up having bricking the device as there might be no solution to recover it due to access rights. ALWAYS have a back up file so you can at least copy the file back and chmod it.
jerk48 said:
After a update for better compatibility for 3rd party app, my Zenfone wont get past the ASUS screen at all.
Click to expand...
Click to collapse
by asus screen, did you mean the ASUS Setup Wizard?
sooty84 said:
you may want to flash your phone back. so this consist of
1) read up how to access to Temp CWM
2) download and transfer the full rom to your SD card
3) do a wipe all partition and go to advanced setting, wipe cache
4) install zip and choose from external SD, point to that .zip file for the full rom and apply.
5) installation may take 10min or so do not switch it off. after installation you are good as new.
I believe this should solve your problem, normal if things get bricked is due to config file error could be [syntax, corrupted, missing, setting].
Flashing should solve mostly of it unless the file that you previously accessed require root and cwm does not give permission to the file. that is a permanent bricking.
As always, newbie should not try tweaking permission required files, you end up having bricking the device as there might be no solution to recover it due to access rights. ALWAYS have a back up file so you can at least copy the file back and chmod it.
Click to expand...
Click to collapse
my problem right now is my pc wont detect my phone. Ive already installed the drivers.
Same thing happened to me when I tried flashing the OTA update with my phone being rooted. You have get into recovery mode on the phone and then use ADB to put the original image back to the device to get it back to stock so it will reboot. It worked for me
sooty84 said:
you may want to flash your phone back. so this consist of
1) read up how to access to Temp CWM
2) download and transfer the full rom to your SD card
3) do a wipe all partition and go to advanced setting, wipe cache
4) install zip and choose from external SD, point to that .zip file for the full rom and apply.
5) installation may take 10min or so do not switch it off. after installation you are good as new.
I believe this should solve your problem, normal if things get bricked is due to config file error could be [syntax, corrupted, missing, setting].
Flashing should solve mostly of it unless the file that you previously accessed require root and cwm does not give permission to the file. that is a permanent bricking.
As always, newbie should not try tweaking permission required files, you end up having bricking the device as there might be no solution to recover it due to access rights. ALWAYS have a back up file so you can at least copy the file back and chmod it.
Click to expand...
Click to collapse
downshift00 said:
Same thing happened to me when I tried flashing the OTA update with my phone being rooted. You have get into recovery mode on the phone and then use ADB to put the original image back to the device to get it back to stock so it will reboot. It worked for me
Click to expand...
Click to collapse
where do i get the stock image?
bratski said:
where do i get the stock image?
Click to expand...
Click to collapse
here is the stock firmware.
https://www.asus.com/Phones/ZenFone_2_ZE551ML/HelpDesk_Download/
its fine if your phone does not talk to your PC now. copy the firmware to your SD card via other means. [card reader etc]
then try my method of flashing it back to original state, you stated that adb dont work, have you tried the temp CWM method yet?
the main goal is to wipe dalvik cache under advanced menu in CWM, and cache partition and all hard reset.
then you flash back your original file.
hope it works for you.
sooty84 said:
here is the stock firmware.
https://www.asus.com/Phones/ZenFone_2_ZE551ML/HelpDesk_Download/
its fine if your phone does not talk to your PC now. copy the firmware to your SD card via other means. [card reader etc]
then try my method of flashing it back to original state, you stated that adb dont work, have you tried the temp CWM method yet?
the main goal is to wipe dalvik cache under advanced menu in CWM, and cache partition and all hard reset.
then you flash back your original file.
hope it works for you.
Click to expand...
Click to collapse
ive read about the temp cmw method and i cant figure out how to go about it. it says on the instruction that you need to turn on phone before running the cai_dat_CWM. how am i going to do this as my phone will only boot to the asus logo? thanks
just figured it out. I need to boot in fastboot so the phone will get recognized. However, the latest build available on the asus website is still 2.17.40.12. I already have the 2.18.40.12 version. The 2.17 firmware can't overwrite the newer build in temp CWM recovery. Anybody knows where i can download the full rom? Z00A-WW-2.18.40.12?
bratski said:
just figured it out. I need to boot in fastboot so the phone will get recognized. However, the latest build available on the asus website is still 2.17.40.12. I already have the 2.18.40.12 version. The 2.17 firmware can't overwrite the newer build in temp CWM recovery. Anybody knows where i can download the full rom? Z00A-WW-2.18.40.12?
Click to expand...
Click to collapse
I GOT THE SAME PROBLEM.
dunno what to do anymore.
sigh...
help me please
Ninjakura said:
I GOT THE SAME PROBLEM.
dunno what to do anymore.
sigh...
help me please
Click to expand...
Click to collapse
here is the link for stock but pre-rooted img for latest 2.18.40.12 firmware,,make sure to download Z00A firmware if you have ZE551ML device.. and if I was not mistaken, you may choose to FULL UNROOT in SuperSU apps to go back to stock rom..
cangcan said:
here is the link for stock but pre-rooted img for latest 2.18.40.12 firmware,,make sure to download Z00A firmware if you have ZE551ML device.. and if I was not mistaken, you may choose to FULL UNROOT in SuperSU apps to go back to stock rom..
Click to expand...
Click to collapse
thanks. problem solved after i followed instructions from this thread, http://forum.xda-developers.com/zenfone2/general/guide-to-apply-ota-bootloop-rooted-zf2-t3127835
bratski said:
my problem right now is my pc wont detect my phone. Ive already installed the drivers.
Click to expand...
Click to collapse
me too, any idea on how to fix it?
sooty84 said:
you may want to flash your phone back. so this consist of
1) read up how to access to Temp CWM
2) download and transfer the full rom to your SD card
3) do a wipe all partition and go to advanced setting, wipe cache
4) install zip and choose from external SD, point to that .zip file for the full rom and apply.
5) installation may take 10min or so do not switch it off. after installation you are good as new.
I believe this should solve your problem, normal if things get bricked is due to config file error could be [syntax, corrupted, missing, setting].
Flashing should solve mostly of it unless the file that you previously accessed require root and cwm does not give permission to the file. that is a permanent bricking.
As always, newbie should not try tweaking permission required files, you end up having bricking the device as there might be no solution to recover it due to access rights. ALWAYS have a back up file so you can at least copy the file back and chmod it.
Click to expand...
Click to collapse
I have same prolem as OP's got.
I've got stuck on Asus Loading screen after install OTA update on rooted device.
I'm gonna try your method.
Thanks
downshift00 said:
Same thing happened to me when I tried flashing the OTA update with my phone being rooted. You have get into recovery mode on the phone and then use ADB to put the original image back to the device to get it back to stock so it will reboot. It worked for me
Click to expand...
Click to collapse
how did u do that? can u give me step by step instruction please?
ty
Did anyone able to fix this problem (stuck at Asus logo and not able to get to recovery mode or connect to the computer)? Thanks!
SAN_MARINO said:
Did anyone able to fix this problem (stuck at Asus logo and not able to get to recovery mode or connect to the computer)? Thanks!
Click to expand...
Click to collapse
Press Power+Volume Up key, After vibration leave Power Button then choose Recovery Mode using Volume keys, if sleeping Android screen appear at Recovery with Error message, Press Volume Up and Power and leave immediately Power Key, it will show you the Recovery Menu, then Reset your device, it will solve your problem.
If I am helped you, Press Thanks button.
k576 said:
Press Power+Volume Up key, After vibration leave Power Button then choose Recovery Mode using Volume keys, if sleeping Android screen appear at Recovery with Error message, Press Volume Up and Power and leave immediately Power Key, it will show you the Recovery Menu, then Reset your device, it will solve your problem.
If I am helped you, Press Thanks button.
Click to expand...
Click to collapse
Thanks!
I already tried it like 20 or more times. The ASUS logo still shown for like 10 seconds and died and came back again (ASUS logo). When I tried to connect it with my laptop, the computer won't recognize the device.
SAN_MARINO said:
Thanks!
I already tried it like 20 or more times. The ASUS logo still shown for like 10 seconds and died and came back again (ASUS logo). When I tried to connect it with my laptop, the computer won't recognize the device.
Click to expand...
Click to collapse
I will try to tell you step by step:
1. Press Power Button + Volume Button
You enter into Recovery Fastboot Option, then Choose Recovery menu using Volume Key (3 Option mostly shown)
then press Power Button (From Recovery Mode), it restart.
2. Then after Restart it shows you (Mostly) Sleeping Android Screen with Error text, then Press First Volume Up Button, and Press Power Button (Power button for a second or two then leave it, IF YOU PRESS MORE TIME, IT WILL RESTART THE PHONE).
3. You can now see the Recovery Menu with Normally appear in other phones also - Reset, Restart, Etc Option.
Hope you will now able to reset your phone...
----------------------------------------------------------
PRESS THANKS BUTTON IF I AM HELPED YOU
----------------------------------------------------------
IS the android recovery menu stored in the bootloader?
Does the bootloader corresponds to the file boot.img on SP FLASH TOOL?
I have an alcatel 7047 xpop c9 (with MT6582M processor) . It power on and automatically goes to android recovery menu and there is no way to let it exit from this mode or to power off because the battery is not removable.
It seems that the problem appeared during an upgrade, because the battery discharged during the process.
Today i tried to use SP FLASH TOOL version 5 in order to write the flash, included preloader, boot, recovery etc., by using a backup for this phone found on internet. After flashing everything i tried to reboot the phone but each time the same menu is shown.
Question: does the boot.img file overwrites the bootloader? How could I understand what is the problem? Could I enable some print or log, even remote logging, in order to better understand what is going wrong?
Yesterday i also tried the upgrade tool from alcatel website (it reloads all the original files but the result is the same).
EDIT: i was able to open the case, remove the battery and replug it, but the problem is still the same: Reconnecting the battery and powering the phone, it automatically goes in the recovery menu.
Wow
Wow, no reply. Is it there someone hereeeeeeeee?
gaucho1978 said:
IS the android recovery menu stored in the bootloader?
Does the bootloader corresponds to the file boot.img on SP FLASH TOOL?
I have an alcatel 7047 xpop c9 (with MT6582M processor) . It power on and automatically goes to android recovery menu and there is no way to let it exit from this mode or to power off because the battery is not removable.
It seems that the problem appeared during an upgrade, because the battery discharged during the process.
Today i tried to use SP FLASH TOOL version 5 in order to write the flash, included preloader, boot, recovery etc., by using a backup for this phone found on internet. After flashing everything i tried to reboot the phone but each time the same menu is shown.
Question: does the boot.img file overwrites the bootloader? How could I understand what is the problem? Could I enable some print or log, even remote logging, in order to better understand what is going wrong?
Yesterday i also tried the upgrade tool from alcatel website (it reloads all the original files but the result is the same).
EDIT: i was able to open the case, remove the battery and replug it, but the problem is still the same: Reconnecting the battery and powering the phone, it automatically goes in the recovery menu.
Click to expand...
Click to collapse
Just discovered your post. Have you solved the issue?
First of all, the recovery image is not stored in the bootloader...whatever you meant by that. It is stored in the recovery partition. The boot.img is NOT the bootloader. It is the kernel. And it is stored in the boot partition. Those questions simply sound like you are trying to figure out why your phone is booting into recovery. Even after you have restored the STOCK ROM using Alcatel's Mobile Upgrade S.
My first thought was that you have no system image or that your custpack partition is corrupted. But those issues would lead to a boot loop or you would just hang on the boot logo and not move forward. Plus you restored the stock ROM. So that's really strange that you're booting only into recovery each time.
However what is more likely is that you are not starting your phone correctly. I once had a lady with the exact same issue. Her phone developed this strange problem where it would only boot into recovery. Her phone was completely stock. She never did anything with her phone except use it like a non-techie would use their phone. She didn't even know what recovery meant. All she knew was this strange menu always appeared when she started her phone.
BUT, when I booted her phone...guess what? It booted up just fine! But with her, her phone would always boot into recovery. You know why? I watched her boot her phone. She had developed a new habit every time she started her phone of inadvertently applying pressure on the Volume UP button while she was turning on her phone...because it was on the opposite side of the phone from the power button.
It's really weird that the problem persists even after you flashed back to stock. If that's the case, my only other guess is that your motherboard is damaged, or perhaps it's not you who is holding down the vol+ button...maybe it's just stuck.
I was trying to load Lineage onto an old One M8, I had just cleared the system, cache and data partitions using TWRP. I then clicked reboot, which I now realise was a mistake. I am now stuck on the HTC logo screen, none of the physical buttons are responding, so i cannot get into bootloader etc. I can't send ADB commands to it, it won't show up on windows file explorer, I can't even turn it off. As is said this is an old phone so I am not worried about losing data, which is probably just as well at this stage!
Any advice would be appreciated!
Kieran C said:
I was trying to load Lineage onto an old One M8, I had just cleared the system, cache and data partitions using TWRP. I then clicked reboot, which I now realise was a mistake. I am now stuck on the HTC logo screen, none of the physical buttons are responding, so i cannot get into bootloader etc.
Click to expand...
Click to collapse
The physical buttons will respond, but you need to hold them for a pretty long time in the current "stuck" state. Do this:
1) Hold vol up button and power button, until the phone restarts (may take about a minute in the current stuck state).
2) Once the screen goes dark to reboot (but before the HTC logo screen appears again - I think you have 5 seconds or so), let go of the buttons, and only hold the vol down button. Do not let go of vol down, until you see the bootloader screen.
3) If you fail to get to bootloader, you simply got the timing wrong. Either started pressing vol down too late, or you let go of it too early. Simply repeat steps 1 and 2, until you get to bootloader.
4) Once in bootloader, simply select recovery, which will boot TWRP. And flash Lineage as you originally intended.
A note on wiping system when flashing a ROM: I know some folks will swear by this, and some guides will tell you to do it. But it is not necessary, and as you've seen can cause some complications. Nothing that isn't easily solved, but may give you headache nonetheless (like this case here).
The ROM install script will wipe system before it installs the custom ROM. So doing it yourself is redundant. And in the case of the ROM fails to install (it happens) you are stuck without a working OS. My recommendation is only to wipe cache, Dalvik and data when flashing a custom ROM (the default wipe in TWRP).
Any perceived "benefit" from wiping system is usually a placebo. In the rare event that the custom ROM fails to boot (or some other issue), you can always go back and flash again, wiping system (as a troubleshooting measure, etc.). Of the years of flashing ROMs (dozens and dozens of times) on various Android devices, I can count maybe 2 times where I felt I needed to wipe system when flashing a custom ROM.
Kieran C said:
I can't send ADB commands to it, it won't show up on windows file explorer
Click to expand...
Click to collapse
This can be expected when "stuck" on the logo screen. adb will only work when booted to a working OS, or alternately when booted to TWRP. Same thing with MTP access (File Explorer).
Pixel 3a XL
I haven't been getting a notification when there is a new monthly update and checking for update button not working either. I am rooted with Magisk and have some modules installed. I have disabled the modules, unistalled the modules and neither worked. I have uninstalled Magisk and checked for update before reinstalling.
Any idea what could be blocking me from getting OTA?
Thanks
You can't take ota's if you have magisk and or a custom kernel installed
you have to restore/ flash the boot img from the factory img your currently on in fastboot on a pc or mac
I've done it many times with these directions. I recently had to factory reset my phone and since I've done that no OTAs.
http://bit.ly/2PTAXj0
Getting an OTA to take while rooted is always hit and miss. I bought this phone in May 2019 and have successfully installed an OTA update perhaps 3 times since owning it.
You are going to have to get very familiar with sideloading the updates. Here is a set of instructions that I created in my "How to Root" thread in the Pixel 3a forum.
If the normal OTA method isn't working - sideload the OTA update
Taking an OTA update should be as easy as the above instructions. However there is another option available to install an OTA update called sideloading. Sometimes the update doesn't appear on the phone in a timely manner and you may want to manually install the update. Other times the OTA update seems to fail for some reason. In the end, you may decide to sideload the OTA instead of trying get it via the update feature on the phone. Surprisingly, it's actually faster to install the update via sideloading than it will be to take the OTA normally. I'll walk through the sideloading steps.....
Optional Step 1 - Uninstall Magisk (so that it restores the stock boot.img). If you find yourself unable to boot into recovery, you will have to restore the stock boot.img. I've run into this issue on some Android 10 images, but not all.
Step 2 - Download to your computer the correct OTA image from here
Step 3 - Connect to your phone via ADB on your computer. You should see the device listed if you type the command "adb devices".
Step 4 - Boot your phone into recovery (type the command "adb reboot recovery").
Step 5 - The phone will have a green android robot with a red sign over it's open access panel. Press the power button and then the volume up button while still holding down the power button.
Step 6 - Select "Apply update from ADB" using the volume buttons to highlight the choice and the power button to select it to enter the sideload mode.
Step 7 - Using your computer, type "adb sideload ota_file.zip" where ota_file.zip is the name of the OTA file you downloaded in step 2.
Step 8 - Once the update finishes, reboot the phone to complete the update process. (See note below about initial boot times).
Step 9 - To obtain root again, please use one of the two root methods listed above
Please note, while the the initial boot doesn't generally take that long there are times when may take quite a while. In extreme cases, I've seen the process take upwards of 20 minutes and longer. I think part of the reason it can take so long is that it optimizes the apps during this boot process. The more apps you have, the longer the process may take. When you take an regular OTA update, the phone will change to a screen where is specifically tells you it is optimizing the apps and counts up as the apps are optimized to give you status updates. When you use the side-load method, it all happens with just the regular boot animation running and without any status updates. Because of this, it is easy to assume something has gone wrong with the boot process while in fact the phone is working through the process normally. If it isn't boot looping (showing the initial power screen before moving back to the boot animation), everything is fine and you just need to be patient and let the phone complete the process.
I updated via sideload. Thank you