Chosen Solution
So, I replaced the camera lense on the main camera and after that, 4 days. the customer comes back, facetime camera does not work. I have tried about 10 facetime flexes and no result on camera. earspeaker, proximity sensor works perfectly. What is this, how do I fix this?
It would be surprising if you had 10 defective FCAM flexes. Still, you should test them in another, known-good device to be certain. However, IMO, you have a logic board issue and you need to start investigating the FCAM circuit. Start with checking all the relevant power lines (see image below).
Then check the rest of the connector (J4503) against known-good values (ZXW).
