SIM Card not registering (?), SIM works in other phones

I’m trying to fix a friend’s S21 over the weekend, and after a while of trial and error, I’m more stumped than when I first started trying to fix the thing. For some vauge history, phone got ran over by a car and was functional up until a few days ago. SIM stopped registering, however phone could register when non-AT&T SIM’s were in it, and had an additional message when no SIM was in the phone at all (went from No SIM to No SIM | No Service). I’ve tried just about every hardware fix, besides opening it up and checking it out, and my buddy said that he had previously tried software-based fixes, though to no avail. Is there anything that I’m overlooking, or can do to try and fix this thing? eSIM is unfortunately not compatible with the phone. would like to spend as little money on this as humanly possible, as while my time is endless, my wallet is not.