Gl-x750v2 Sim card cannot be registered

I’m having trouble with my GL-X750V2 that’s been working great for the past 3 months on the T-Mobile network. All of a sudden this Saturday, I lost network access and I have a message that says, “SIM card cannot be registered. Please check: 1. You are using the compatible modem for your carrier; 2. Whether a specific APN or data plan is required.” The SIM card is still functional in my smartphone; I tried a different SIM card and different APN settings with no success. I don’t know if anybody else has had this issue. The SIM card has a basic unlimited data plan for talk, text, and data with a 5 GB hotspot.
Any help and advice would be greatly appreciated.

Have you upgraded to firmware 3.215?

Yes, it is running the latest firmware 3.215. That was one of the first things I did when I couldn’t get anything else to work

Thank you though