MBB troubleshooting is pretty straight forward. Aside from issues that may arise such as weather and outages, an issue with MBB always comes down to 3 things; The network, the SIM card or the device that’s using it.
If you’re having issues with the connection, try rebooting the device you’re using. This can be done by powering it down and removing the sim card for 5 minutes, then reconnecting the sim and powering the device back up.
Failing that, it’s best to test the sim card in an alternate device, such as a smartphone or tablet. This will help you determine if the issue is with the hardware or the network.