I replaced my old battery with the one I bought here in iFixit. I replaced the battery according to the instructions of this guide (Using a guitar string did the trick when removing the battery) and finally assembled the sensor ribbon. Turned on the phone and SURPRISE! Error, Touch ID Does Not Work. I was disappointed, in the most part because I was extremely careful, it's not my first repair, and I did not break the ribbon, the Home Button was working properly.
I spent 4 hours re-seating the ribbon and putting in place the metal bracket.
For you guys, who have lost Touch ID but didn't break the sensor flex cable AND the Home button works, I thing I have found a SOLUTION:
As you can see in the picture (link below), a grounding Tip under the screw MUST be in THIS POSITION. If misaligned it will not work. Mine was misaligned during the display disassembly (STEP 16) and this was the solution. A smile returned to my face.
