In the webadmin, have you checked the box that enables remote access in Plex?
As Alex said, TCP-UDP may help too, I have mine set to allow both protocols.
By chance, are you using a domain to access your server? (plex.mydomain.net)
As Alex said, TCP-UDP may help too, I have mine set to allow both protocols.
By chance, are you using a domain to access your server? (plex.mydomain.net)