Are you using a correct APN or have you tried to set APN manually? This can be done in the WebUI by navigating to Network -> Interfaces and editing mobile interface settings?
Does the M2M card has access to 2G, 3G, 4G networks and in not limited to, NB - IOT or LTE CAT - M1?
Does your ISP have network coverage in your area?
It would be helpful, if you could provide a troubleshoot file. Please, replicate the issue, then access router's WebUI, go to System -> Administration > Troubleshoot section and download troubleshoot file from there.