Why do I have no service after motherboard replacement?

I have a pixel 5a that had the black screen issue where the screen just died one day but the phone itself still worked. I looked it up and there was a special extended warranty just for that issue because I guess it is a common enough problem. I took it in to the Asurion repair center and they replaced the screen but it still didn't work so they replaced the motherboard. They told me that it was a 95% chance it was the screen causing the issue and about a 5% chance it was a motherboard problem. Once I got home I noticed that I didn't have any service even though the sim card was inserted. I tried the same sim card in another phone and it worked just fine. I contacted Asurion, Google support, and Google Fi support. Google support was no help whatsoever and didn't even offer to replace the phone because even though the blackscreen issue was still covered under the special extended warranty, the signal issue wasn't although it was the blackscreen issue that caused all this in the first place. Asurion replaced the motherboard two more times and it still doesn't work. Neither Google nor the Asurion repair place want to own up to the mistake and take care of fixing this so I am left with a paperweight. I'm hoping that someone here knows what is wrong. Is there an antenna that is separate from the motherboard that may have gotten detached? Or maybe some other fixable issue? Thanks in advance for any help!

Pictures of tab that was covering contacts and the motherboard contacts that it should have connected to.