I've always had problems with plex not being able to find my server despite forcing it to use port 32400, even with a machine exposed directly onto the internet, even in three different continents on different machines... It always finds a way to not work.
Now, it won't even install. I get to the first configuration page after the upsell screen, and then click next to take the defaults, and it just says "There was a problem saving these settings"
If I just reconnect back to /web/index.html, it goes to the main plex page, but in order to do anything I have to sign in. As soon as I sign in, it starts passing through to app.plex.tv instead, which of course can't see the server, which I can no longer configure since connecting directly to it passes through to app.plex.tv, which can't see the server... You see the dilemma. So I have to uninstall the whole thing and then try again, with the same results.
Logs don't seem to be of much help. Permissions look fine. I'm running plex server 1.1.3.2700 on freshly installed Ubuntu server 16.10, no antivirus, with and without router/firewall.