Did you just receive your modem, but it doesn’t work? Do you see a red light on the modem?
Just do a check check if the SIM card is correctly inserted.
It could be that the SIM card is not inserted properly. Just remove the SIM card from the bottom of the modem, check the right way how to insert the SIM card and replace it in the correct way until you hear a small click.
Do you already have your modem for a while and suddenly you have a red light?
Go to MyTADAAM and verify if your subscription is still active. Maybe your payment didn’t go trough. Just make a valid payment and you are back online!