What's the server's hostname? If it's the same as the domain that's not working, perhaps you're running into this bug [0]? If that's the case, then adding

  # /etc/systemd/system/systemd-resolved.service.d/override.conf
  [Service]
  Environment=SYSTEMD_RESOLVED_SYNTHESIZE_HOSTNAME=0

[0]: https://github.com/systemd/systemd/issues/34897#issuecomment...