Default What could be causing my no service problem?

After restoring my lost IMEI values i still have no service. Even though I am clearly receiving a signal, I have no service when I try to do anything.

Occasionally when i turn the phone on ill get about 5 minutes of 4g but no lte, but this eventually decays into nothingness.

What could be causing this problem? Im baffled and in need of a working phone. I unrooted, returned to stock, and updated to latest firmware ota and still nothing.