It has been observed with some AT&T SIM cards that the Digi EX12 will obtain an IP address from the AT&T network, but the Digi EX12 will not route any traffic over the Mobile interface (e.g. - to the internet). The issue is due to the APN "attm2mglobal" not being provisioned for the SIM card.
NOTE: This issue is only present on the Digi EX12. Other Digi routers are not effected by this issue, even if the APN "attm2mglobal" is not present on the SIM card.
There are 2 ways to correct this problem:
1) Work with AT&T to have the APN "attm2mglobal" added to your SIM card and service plan. A reboot of the device may be required after the APN is added to the SIM card and service plan.
2) Issue the the following AT command to the device: modem at "#lwm2mskip=1"
This command should be issued at the Admin CLI on the device. To access the Admin CLI, see the following documentation:
Local Device Access
Using Digi Remote Manager
NOTE: This is a one-time command, and will persist throughout reboots/power cycles of the device.