If your phone is stuck in a boot loop or the OTA fails, the official HTC ROM Update Utility (RUU) is the best recovery tool. Steps to Follow:
If an update is available, follow the on-screen prompts to . Firmware Change Update on HTC One X9
Ensure your HTC One X9 has at least 60% battery to prevent it from shutting down mid-process. If your phone is stuck in a boot
This is the standard method provided by HTC. It is safe and does not void your warranty. Connect to a stable . Go to Settings on your HTC One X9. Scroll down and tap on About . Select Software Updates . Tap Check Now . This is the standard method provided by HTC
Before attempting any firmware modification, ensure your device is prepared to prevent data loss or hardware failure.
Copy the file to the root directory of a microSD card (not inside any folder). Insert Card: Put the SD card into your HTC One X9.
If the phone is functional, enable USB Debugging in Developer Options.