Setting up AT&T sim card with Raspberry pi and Hologram NOVA

Hello all,

I have been trying to set up my Hologram Nova Cat-M1 &NB-IoT with an activated AT&T Sim card. I have visited this link https://support.hologram.io/hc/en-us/articles/360035697553-Use-a-third-party-SIM-with-the-Hologram-Nova given to me by support. I have changed the APN to NXTGENPHONE but am still running into the same error of having an unregistered sim card. I do not understand what other changes I need to make or what those changes are. I have the hologram model connected to a Raspberry Pi Zero 2W. The raspberry pi has the the hologram software installed. if you have a solution that would help me out a lot.