I host a Plex Server on an AT&T 1Gb Fiber connection. I had to move the server to another location in the house and had bandwidth issues, so I bought the RE715X to extend network range. The extender setup well and is doing it's job, but the Plex server's Remote Access configuration now is unable to connect (see image).

When I switch back to my AT&T Modem/Router connection, it works fine. I thought it might be a port forwarding issue. 32400 is open and mapped to the hard IP of the wired connection, so I mapped 32401 to my Wi-Fi connection. Same problem. It says it's connected successfully but within moments fails.

For reference, both the AT&T Modem/Router and the Tether app for the range extender display the same IP4 and MAC addresses. So I'm confused.

Can someone help me iron out configuration so that I can host Plex properly across the range extender?