If you get this message - " Failed, unable to complete Touch ID setup. Please go back and try again." Then all you have to do is plug your phone into computer, once itunes is opened, put your phone in DFU mode and reset your phone. The phone must be in DFU mode.
This has happened twice now on 2 different iPhone 6 after a screen change. EVERYTHING works for a few days and then ONLY the earpiece stops working. (Proximity sensor, front camera, rear camera ALL work. I have tried replacing the earpiece but still no sound.