HTC released new software update (build 1.28.617.30) for HTC U11 with October 2017 Android Security patches. Based on the Android 7.1.1 Nougat, the new HTC Sense 9 firmware updates unlocked US variant HTC U11 to software version 1.28.617.30. This is just a security update, plus general bug fixes. If you owned this device, you will get the OTA (over-the-air) update in the coming days.
You can also update your HTC U11 to new software version manually by downloading the stock HTC firmware file (1.28.617.30 RUU.exe) to your computer. For example, if you are outside of Wi-Fi coverage and unable to download the OTA update or the OTA update is not found due to some unknown reasons, then you can sideload the update manually via HTC Sync Manager.
If you have not received the OTA notification for software version 1.28.617.30 on your HTC U11, then check it from the Home screen tap All apps > Settings > About > Software updates > Check now > Download.
If update found, download it and once the download is complete, tap the System update to begin the upgrade process. After updating, your device will reboot.
Note: For manual installation, you need to download the massive HTC Sense firmware file (RUU.exe) (around 1.8GB) to your PC and install HTC Sync Manager on your PC.
How to Install Firmware update on HTC U11 manually
1. Download and install HTC Sync Manager on your PC (download here).
2. Download HTC U11 Sense 9 1.28.617.30 RUU.exe update file to your PC (download here).
3. Connect your phone to your PC. Once the device is properly recognized, navigate to RRU update exe file and double-click on the exe file. It will launch the system update wizard.
4. Follow all of the system update wizard instructions shown on your PC. Once done, click Finish in the wizard and your phone will reboot.
5. After rebooting, open Play Store, tap the menu icon, then select My apps and ensure all installed apps are updated. (Source – HTC)