Flash through Fastboot.
1: download the firmware you fit their machine parameters and rename the new file to download to firmware.zip, then copy it back to the Fastboot folder on the C drive of your computer.
2: Turn CMD -> type cd c: \ fastboot, and put the phone in bootloader → Connect the phone to the computer, ensuring USB Fastboot red line currently offline.
3: For S-ON machine must relock Bootloader Light: fastboot oem lock → Enter
(The machine will restart, go back Bootloader check relock it was not, if OK then continue)
– Step 4: Put the computer to the flash mode Ruu: fastboot oem rebootRUU → Enter (HTC ONE will show white HTC logo)
5: Flash Firmware 1st: fastboot flash zip firmware.zip → Enter
6: Flash Firmware 2nd: fastboot flash zip firmware.zip → Enter
(Wait for it to run for about 1 minute, press Finish Fastboot screen on your phone but still running then you just let it be. Use the Power button to reset the phone always is.)
Method 2: Flash by Hboot in Bootloader
1: relock Bootloader.
2: Rename the Firmware File 0PL2IMG.Zip (0 here is 0) then copy it to the memory card.
3: Launch into Bootloader machine will automatically load selected Hboot 0PL2IMG file .zip (to the loading bar top right corner of the screen), when the flash is complete the machine will reset.