I'm trying to use a new AT&T SIM card with a GL.iNet MiFi and I can't seem to get it working. I'm switching from a TMobile SIM card that does work. I've installed the luci-proto-qmi package and created a new QMI interface, using no authentication and the APN 'Broadband' (as instructed by the carrier). All I get is an error that says 'call failed' when this same setup worked with the TMobile SIM card. I get the same error when I run "uqmi -d /dev/cdc-wdm0 --start-network --apn broadband" from the bash shell.
I emailed GL.iNet support to ask if maybe I need a different modem card (the modem is installed in a mini-PCI slot and was one of a few options that was supposed to work with TMobile). They replied with the message: "For AT&T network, it is not an issue with the modem but an issue with their network." and sent me this link. Unfortunately, I am unable to send AT commands to the modem. I've read through this page, and skimmed this manual but running "socat - /dev/cdc-wdm0,cr" and sending "ATI" returns nothing, so I'm clearly missing something.
I'm using the latest release of OpenWRT with all default packages up to date.
Any and all help would be appreciated.