It is wise to be in the latest firmware. You could either do a remote update if you have a working internet in the MOFI router by going to System and then remote update and perform remote update. If you want to do a manual upgrade (if you do not have a working internet in the MOFI router), follow this video tutorial: www.youtube.com/watch?v=7g8SGYDNVbw
At this point make sure the SIM is inside the router. Now log into the router and go to Network and then MOFI internal modem and then all the way to the bottom of the page click on Press here to reset the Sierra module. Once the router is up, perform a factory default. The internet should work automatically. If not, make sure the APN you are seeing is correct You can check APN from MOFI Internal Modem, all the way to the bottom of the page you should see your current Access Point. If we are good on that side, go ahead and check your signal strength. Go to Overview from the top left-hand corner on the list. On the middle of the page, click on Check Signal Strength.
If the signal isn’t good enough, you can try to perform band lock as well. To perform band lock, follow the instructions located in the Knowledgebase for "Band Lock"