After change of display, NFC doesn't work.

Hi! So i replaced a display for a friend, and there were stripped screws on his heatshield from a previous repair shop, so i just told him it will work without it for a few days, and bought a new one. And now, after i changed the display, today he called me, that his Apple Pay won’t work, for some reason. Might that be an issue related to the heatshield, or should i try replacing the antenna? I can’t even check if i accidentally unplugged the antennas somehow now. I’m really confused, and feel really bad. What do i do, and what’s possibly the issue?