“User could not be authenticated. This IP appears to be having trouble signing in to an account”

Just getting started with Plex. I have a paid Plex account. I've installed Plex Media Server (version 1.1.3.2700) on my Mac Mini running El Capitan. I can log-in to the Plex website just fine with my account. When I attempt to log-in on the Plex Media Server, I continually get an error, “User could not be authenticated. This IP appears to be having trouble signing in to an account”.

I haven't once been able to claim this server by logging in. Here are my logs: http://pastebin.com/J2URw3vV

Any ideas? Really trying to get this to work.