Device configurations or software can sometimes cause connectivity to fail. This includes the application software and the GSM module/ chipset and its firmware as well.
If this SIM and device combination has worked before but not anymore, make sure you have not changed any configurations. Update the firmware to a previous version.
If it is a new device you are using for the first time with the SIM/eSIM and you are experiencing issues, check the below items:
Are you registered to the network?
Try the SIM in a different device, preferably a different model as well. If it works, then it’s likely you are facing a device specific issue. Using a mobile handset can be convenient & quick to verify plug-in SIMs’ functioning. For eSIMs, use a different IoT device, if available.
Are the data settings entered correctly?
The basic settings for data connectivity are:
Cellular Data is ON
Data Roaming is ON
APN is configured correctly
Bearer Independent Protocol
MO & MT OTA (binary) SMS processing