Issue with Vortex V3 and AT&T SIM card

I was wondering if anyone has had an issue with the V3 and their AT&T SIM card?

After inserting my AT&T SIM card into the Vortex it doesn't seem to recognize the SIM card at all. It's the SIM that came with my iPhone and in which I've used in my Qin F21 as well. The V3 recognizes the T-Mobile SIM card it came with but swapping it over to mine has not worked at all.

Let me know if you can be of any help!