Hello,
Thank you for reaching out!
Is the DNS server added to the LAN interface? Were you able to verify that the DNS server itself is reachable?
I'd like you to attach a Troubleshoot file. It can be generated by navigating to System → Administration → Troubleshoot.
Please attach it to the original query. It will only be visible to Teltonika moderators.
Best regards,
DaumantasG