Registration denied using SARA R410M

I am using a Hologram SIM with a Sodaq Ubee R410M-02B and am having trouble registering it with the AT&T hologram network. To troubleshoot, I have been using a Xbee explorer-type board and Ublox’s M-center program. Upon power up, everything looks great. It says that the modem is on the AT&T hologram network with good signal strength and “AT+CEREG?” returns with “0, 5” indicating it is registered. However, “AT+CREG?” returns with “0, 3” and a change in network status to “registration denied”. This is a new issue that popped up since I last used them two months ago. Thanks in advance for any help!