It’s most likely someone did an amateur screen repair and broke the cameras ribbon cable somewhere. There’s a plethora of sensors and it happens to be software locked to the phone at factory. So you can’t replace it and maintain full functionality. Due to this the person not only loses faceID functionality but they also lose the ability to use Apple Pay, or store information in the Secure Enclave chip like credit cards, tickets, insurance etc.
It’s most likely someone did an amateur screen repair and broke the cameras ribbon cable somewhere. There’s a plethora of sensors and it happens to be software locked to the phone at factory. So you can’t replace it and maintain full functionality. Due to this the person not only loses faceID functionality but they also lose the ability to use Apple Pay, or store information in the Secure Enclave chip like credit cards, tickets, insurance etc.