I would set up a Wireguard connection just to rule out problems with the router. If it works, it means that the domain is correctly configured and the router allows the connection. https://wiki.omv-extras.org/do…v7:omv7_plugins:wireguard
Once this was verified, I would start from scratch to configure the NPM or Swag container following the recommendations in this document. https://wiki.omv-extras.org/doku.php?id=omv7:docker_in_omv