My proximty sensor does not work. after flex repair

i built this phone from nothing, everything works fine, but its very annoying that whenever i answer a call i keep pressing buttons like " put on hold" or "mute" i changed the cable multiple times without any luck, but i notice that when i have the cable not mounted in my phone, the proximity sensors did not work at first, then i pulled the safety tape of that golden square thingy, then it started working fine, still not mounted in phone. Then i mounted it in the phone again with no luck... i also tried removing the filter on the glass to see if it worked, so the sensors can see straight trough clear glass, but no luck.. i think the problem may be in that gold colored sqaure thing? i have no idea what it actually does :/