Help with Connecting my EC-25A to my AT&T Sim Card

I have a PCB board that has the Quectal EC-25A chip. The PCB board has a SIM card reader soldered onto the back. I went to AT&T and purchased a SIM card to start running the system on its own network. I put the newly activated SIM card into the reader, but the system isn’t recognizing a SIM card on the network. I am probably missing steps as I am new to this, so what should I do next?

PCB board with the EC-25A chip: thumbnail-1 — ImgBB
SIM card holder on the back of the PCB board: thumbnail — ImgBB

I appreciate any help provided :slight_smile: