problem in mine was also something with the sensor behind the button, i guess it's just falling a bit short on distance between the sensor where the button is connected and the actual physical button causing it not to reach and put pressure i'm not sure. i ended up sticking a small cut up piece of rubber strip (or bumper) found on the logic board of another 4s as mentioned in step 24. i also taped over it with a small piece of duck packing tape. i needed to loosen and fiddle with the two screws that go in the power button bracket shown in step 26 until the button 