Plex Web GUI Won't Access/Add New Server

First, I've got a Netgear R9000 router with built-in Plex. I had been running that until I recently finished a FreeNAS 11.1 server build. My issue has many data points:
I installed plex on the FN 11.1, and was able to access it through the GUI (but was never asked to log in - it just went straight to ?my? account).
I then logged into the Web interface for my "old" plex and disabled it.
I changed the manual port on the FN 11.1 machine.
I proceeded to spend three days adding all of my media and playing files, but couldn't get remote access working.
I restarted the plex, thinking that would fix the issue.
When I logged in with my full credentials, it only showed me my old server was offline - the new server and all of my libraries are missing.
I've re-enabled the "old"Plex on the router.
I'm literally able to log into the local web interface on both machines - the R9000 and the FreeNAS. My history shows that the old and new machines have connected previously.
A friend is sharing media with me, and his machine is the only one that I can see right now.