State Searching indicates that the router is not even able to register to the operator.
Could you try the SIM card with another device, for example, smartphone, to check if it has data connectivity?
If it does, reinsert the card to the router, wait for a few minutes, then generate a troubleshoot file. To do so, please access router's WebUI, go to System -> Administration > Troubleshoot section and download troubleshoot file from there. Attach the file by editing your question. The logs may provide more details to the issue.