Uh, that’s interesting. I’m having the exact same issue. Tried everything, uninstalled and installed Plex, but ended up with the “server not found” message. It’s totally broken (and btw: I am kind of a system administrator and not a noob). It used to work fine, but stopped working somewhen beginning of march. Also on a Synology DS 415+, used to work with Plex Server 1.13.x, now on the latest stable 1.14.x. Lifetime Plex Pass User.
But I find it very enlightening, that all of a sudden, there are a couple of these posts popping up here, see Plex server unavailable all of a sudden
(edit)
And here: Http://192.168.0.32:32400 cant find server
