Chosen Solution

I took out the old camera assembly to put on a new screen, but the two sensors (ambient light and proximity sensor) will not click back in no matter what I do, so I can’t put the earpiece speaker back on.

Must be 4 reasons for that cause
1. Dust on your screen hole where proximity sensor aligned

2.Flex cable is damaged

3.Front camera connected deformed

4.Proximity sensor circuit demaged
So to figure out the source of your problem first take new camera if does the same try to test it while the camera is out from LCD/Display let it free from obstacles because proximity sensor do sense near objects,if no solution try to do cosmic inspection on front camera connector (it maybe deformed during disconnect front camera)….if no any deformation do measure diode value of front camera connector….found any abnormal try so solve it,if everything is normal do measure Voltage while connecting front camera while activated or while making a call for proximity sensor to be activated….if all are normal replace front camera connector……..