just covert unit to developer and flash latest dev RUU. Need to be S-OFF for this to work. I used sunshine to get (S-OFF)
Converted to Developer Edition:
Changed MID to: 0PJA11000 (ADB commands to convert)
Changed CID to: BS_US001 (ADB commands to convert)
Download the developer edition ROM for *M9* from the link, you are set. HTC One M9 3.35.617.21
http://dl3.htc.com/application/RUU_H...170.1480969736
install RUU via clicking the downloaded EXE
DO NOT EVER GO S-ON.
Worked great currently on 4.19.617.1 OTA updated no problems.