proximity sensor not working

Ok here is my ordeal.. Changed a screen on iphone 6. not my first one, I have a side gig doing repairs. I changed the screen and the proximity sensor does not turn the screen blank when put to the ear. So I made sure it is seated properly in the plastic piece, I checked the connection of the cable, and even replaced the proximity sensor with camera flex cable. It still won't turn off the screen when putting the phone to an ear. ANY experience, tips, helpful tactics would greatly be appreciated at this point.