Hi Shawn, I suppose you've tried already with a different sim card from another operator. What I would try
* first is to eliminate few variables, like if the phone can read the sim ok. I have 2 ideas: insert a sim with a PIN code active or use an app, like Zinny, where in Internet screen you can check what is the Sim Status. If the status is Not present, could be from the sim tray or contacts.
* If the phone read the sim (Sim Status = ready), I would check if the phone detects any sell (with G Net tracker). If yes, then the antenna is working.
* If the antenna is working, then I would check if the radio bands supported by your phone are used by your local operator (some models have the radio modems adapted to specific areas). Also Reset to Factory and checking if the APN is correct might help
Let me know if any of this helped.