Connect your HTC One M8 to your PC using a reliable USB cable.
If you installed CyanogenMod or LineageOS years ago and want to return to the official HTC Sense UI. htc one m8 stock rom updated
HTC provided the One M8 with approximately two years of major firmware support. The official stock ROM progression included: Android 4.4 KitKat : The launch version, featuring HTC Sense 6.0 Connect your HTC One M8 to your PC
Verdict: If you are just restoring your own device to the exact carrier version it shipped with, you do not need S-OFF. Just lock your bootloader ( fastboot oem lock ). The official stock ROM progression included: Android 4
The M8 vibrated. The screen on the device flashed a warning: Updating System... Do not disconnect.
What is your specific ? (International, Verizon, AT&T, Sprint?) Do you know if your device is S-ON or S-OFF ?