Weak Signal after iPhone 11 housing replacement

Hi, a while ago I discovered my broken iPhone 11 in a drawer. I didn't repair it because I bought a new one right away and somehow forgot about it. Now I figured this is the perfect opportunity to learn how to repair phones, so I ordered a new housing and replaced everything. To my surprise, the phone turned on and everything works perfectly, except for the cell signal.

After inserting the SIM card, one line appears for a moment, but before I can dial the call, I get a NO signal message. I assume there will be a problem in one of the antennas. I just don't know which one. This is my first repair of any electronics ever, so I apologize if it's obvious to you at first glance from the photos I've attached. Thanks so much for the replies and advice..