AP-1300 Sim Not Registered

We use the AP-1300’s for our business and I am currently trying to setup one on AT&T but I keep getting the message “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.” Which I am used to seeing all the time but once I set the APN and do a modem reset it typically works but this time I cannot get it to do anything at all. It shipped with 3.212 firmware and I have reverted the firmware, refreshed the 3.212 firmware, tried multiple SIM cards that I know are working in other devices but this one is about to get booted right out the window. I even tried changing the IMEI’s 3 different times just incase that was the issue. Anyone with any insight on what its doing?

First can you upgrade to 3.215?

Second, do you have any info about the sim card, e.g. what plan is it, does it need special apn, pin, etc?