Thank you for your response VykintasKuzma.
I am not sure exactly what is going on, but it happened recently to another TRB140 modem I have on the field. It attended site and did a reboot and it did not work, it only worked after holding a pin in the 'reset' slot to reset the modem (I am assuming this is what resets to factory settings) which then started it flawlessly. What do you think the problem is based on the scenario provided? Is there any way I can check what the problem is in a log maybe?
I will follow the instructions provided, but is there an alternative to 'reset' rather than 'reboot'?
Unfortunately right now without the SMS commands working, I have no choice but to go onto the field and manually reset the device to reconnect to the internet.