There could be a couple of causes for this issue:
The modem that you've used is locked and doesn't accept the SIM card. You will have to decode it or use a compatible SIM card.
The SIM card doesn't have the Internet subscription activated.
You are in a zone where Internet coverage is low or doesn't exist at all.
As you can see, there could be various causes, but I recommend starting with the second one. Contact the carrier's support section to obtain additional details.