Cant return to stock htc sense after flashing lollipop htc one m8 att topic

so my charging port has a factory defect and I need to return to stock htc sense before I send it in,
I flashed skydragon rom and i tried to return to a backup and it keeps giving me errors
i've tried everything from a ruu to nandroid backups i am stuck and i have no idea what to do no other roms will flash except cyanogenmod and i cant flash anything from there either please help!