Remote access not working despite server settings claiming all is OK!

Thank you for your effort in trying to help me resolve this one.

I have cleared the Network settings back to default and only have remote access enabled now:

On https://plex.tv/api/resources?includeHttps=1&X-Plex-Token=[token_here] I see this info:

All the masked details are correct. So for the I can see my public IP and the same port as opened in USG.

I can access my PLEX using the public IP and port without no issue - so the port forwarding works without any issue:

BUT as soon as I try to access my PLEX using https://app.plex.tv/desktop/#!/ then PLEX is not able to access the server:

What else could impact that Plex acts up like this?