Chosen Solution
I have just completed the front panel replacement. The Touch ID extender flex attached to the LCD metal shield was a pain to remove. I removed it leaving the small metal plate and refitted to the panel. At first boot, Touch ID was working but the next time when I tightened everything up it refused to initialise the sensor. How important and why is this small metal plate important? Could it be that I damaged the flex behind the LCD and could installing a new cable not button fix the issue?
Go to settings,general,reset and choose rest all settings which is the first option. After that set your Touch ID
