If you are having trouble with receiving the OTA updates, then it’s most probably down to absence of stock recovery, or, because of any changes in system partition when it needs to be 100% untouched stock partition. Stock recovery and untouched stock system partition, mounted as read-only, are two pre-requisite of One M9 OTA updates. Lack of any one would do no good. We’ll discuss how to fix both of these issues, you do need both of them fixed to get OTA update working.

Know that both of the above causes are possible only if you installed, or at least tried installing, a custom recovery like TWRP on your phone. Because that removes stock recovery when installed, and if it’s a version prior to 2.8.6.0, then that version mounted the system as read-write, something which breaks down compatibility of OTA updates. You need that as read-only. Note that even if you fix one of the cases below, you’ll not get OTA update fixed. You need to fix both cases discussed below.

Case 1: Stock recovery is absent

If you have installed any custom recovery, whether it’s TWRP or CWM or any other recovery, you need to remove it and install the stock recovery back.

Make sure you use the exact stock recovery that matches the build no. of your current firmware that’s installed on your phone. Otherwise, it could brick your phone.

If you cannot find the stock recovery for your current build no. of One M9, try finding the RUU file of the firmware that’s installed on your device by using its build no. as reference. Installing the firmware back would bring the One M9 to factory state, and would remove all custom recovery and system partitions, and make it ready to receive OTA updates.

Case 2: Changes to system partition, or mounted as read-write

For the second issue, when the system partition has changed, you need to have a back up of stock system partition, which you can now restore. Now the backup of stock partition is possible currently only when you use beta version of TWRP recovery, which keeps system intact from any changes by keeping its mount mode as read-only, the default one. Any version prior to 2.8.5.0 of TWRP changes the mount status to read-write, which breaks things, while the 2.8.6.0 version keeps system as read-only, but doesn’t back up the stock system which you need for restoring when you’re looking to receive OTA updates.

  • So, if you have the back up of stock system partition of your current firmware, then use this guide to restore the system backup.

If you don’t have the backup of stock system, which could be the case most probably, then flashing the RUU remains only chance. RUU would restore the One M9 back to factory state, ready for OTA updates.

Summary

Although chances of it are slim, but if you knew about the issues of TWRP recovery with HTC One M9, and then you took care to install a beta version of TWRP recovery (newer than 2.8.6.0) to keep system’s read-only mount status as intact, and then took a backup of it, you can restore it back now using fastboot method, and also install the stock recovery back, to get the OTA updates back.

Otherwise, your only hope is flashing the firmware back using its RUU. Make sure it’s for your One M9’s model no. exactly.