I just updated my Plex Server to 0.9.15.2, and at the same time updated OS X to 10.11.3 from 10.11.2. Now my server is not available outside of my network. Turning the firewall off doesn't make a difference. It previously worked great, and other services on the same machine are accessible from the outside.
The only clue I have is that I tried signing the server out and in again, and had a bunch of trouble signing in, but it eventually worked.
Does this sound familiar to anyone?