I had similar issues, I tried everything, then I found this site and found tools and parts that may fix the issue, so I just ordered it all. Then in this forum I read about this IMEI, and I didn’t know much about so I looked it up. And did what I found in this forum :
Go to your phone’s dialing keypad and dial *#06#. Do you see the IMEI displayed?
I didn’t see anything come up, so I tried it a few more times and still nothing. I decided one more attempt at resetting the network settings. While it rebooted, I wasn’t paying attention, then I heard a noise and a message came up saying I had voicemail. I got cell service back, I hope it stays, it’s been almost a year without this phone.
I haven’t cancelled my order,, just in case.