In the image you can see the camera has lifted out a bit. Mine did this too, because the old screen had levered it out. To push the camera back into position you need to insert a fine tool behind a small metal spring contact because it catches on the camera's casing otherwise. This little spring is to the left of the metal case, between the camera and ribbon.

On reassembly the microphone nozzle really didn't want to go back into the new rubber seat, and then the ear-speaker had the same problem. I found holding everything in place and squeezing the whole assembly together with the backing plate before screwing was all i could do, and hopefully that works ok. The speaker phone function never gets used anyway, and the ear-speaker is quite loud.