Having trouble with Remote Access on Mac

Server Version#: 1.16.5.1488

My set up consists of a Netgear C6250-100NAS Router (with UPNP enable) and an AirPort Extreme in bridge mode.

I tried to set up a port forward in the NetGear router settings but the internal IP address calls for a 192.168.0.X prefix range, not a 172.27.35.X range.

What am I doing wrong?

-m

sounds like possible double NAT.
Are you sure your airport is in bridge mode?
Also disable UPNP its either UPNP or port forward.not both.

Might need to setup port forward on netgear to airport and airport to plex server.
or can you plug your plex into the netgear direct?