It's hard to say what could be causing the issue here. Could you clarify if you started experiencing issues once the Wireguard instance was set up?
If not, then the Wireguard instance is most likely not related.
A few things to check:
- Navigate to Network → Interfaces → General, and on the LAN interface add custom DNS servers 126.96.36.199 and 188.8.131.52;
- In the same Network → Interfaces → General menu, edit the mob1s1a1 interface, and in the Advanced Settings, change the Override MTU to 1420;
Have you changed any of the firewall settings? If so, try reverting the changes.
If the options mentioned above do not help, please replicate the issue, navigate to System → Administration → Troubleshoot and generate a troubleshoot file. This file can be attached to the original post and will only be visible to Teltonika moderators. It will give us some insights into what the issue could be.