After replacing screen, mic and earpiece don't work for calls?

A friend came to me with an iPhone 4s that has been sitting in a drawer at home for about 6 months now. The issue was that the screen had cracked 7 months prior, so he got it fixed at a market stall, and when he picked it up and got home, he discovered the mic and earpiece not working and he could not pick up wifi, so he threw it in a drawer. I said I'd take a look at it.

Now I have completely disassembled the phone and screen, and checked all ribbons and connections as reassembling. When you call out or receive a call, there is absolutely no sound coming from the earpiece of the phone or any sound coming from the working phone, suggesting the mic isn't working. I swapped out the earpiece and tried that, still no sound. Then I had an idea. I tried to make a FaceTime audio call. No problem, perfect sound coming from the earpiece and the mic worked perfectly. Hung up. Tried to make a normal call again, connected, but nothing.

Can anyone help?