Front cam not working after screen repair

I repaired a iPhone 15 Pro Max last week and placed a new screen. I had no passcode so could not test it.

Now the iPhone has come back and the front cam isn't working. In the camera app it just doesn't switch from back to front camera. And in other apps or configuring face id it is just a black screen.

I tried restarting the device and resetting the settings. Also updated the device with IOS18 from 17. I also ran diagnostics and in the camera image and face id test it says that the camera is not connected. So I opened the device and reseated the connectors. Still nothing, than I cleaned the connectors on the mainboard as well as both flex cables but still nothing. I could also find no damages on the flex cables or camera modules.

I also connected the device with 3utools and the verification report gives a score of 100 but under front camera it says N/A (not available).

Anyone have any idea what the problem could be? The device was severely dropped to be fair and outside of the touch screen the LCD itself was also shattered.

Do you think replacing the front camera incl. the IR camera would work? I can order a pulled part (so it's original) but will the face id work again after running the repair assistant?

Thanks in advance!