iPad can’t connect to cellular

IPad can’t connect to existing cellular plan. I activated it and thought that should do it but after about three weeks I’m still not connected. It has a phone number that is local for this area.

I got on the myAT&T app and got support from Nathan S. After doing so work on his end he had me reboot the device. It still won’t connect. I’m sure there is more I need to add but can’t think of it right now.