Hello,
What firmware version is your device is running?
Could you attach a troubleshoot file to your question? Make sure the issue is present, the WAN connection has gone down, came back, but the router is not capable to reconnect, then access router's WebUI, go to System -> Administration -> Troubleshoot section and download troubleshoot file from there. The logs in the file might provide more insight into the issue.
Attached files are private and visible only to Teltonika Moderators.
Best regards,