I needed to move the Plex server to an area that is far from the router. Originally, I had ip 192.168.1.251 on the NIC, I disabled the NIC and used IP 192.168.1.252 on the wifi and changed the firewall to forward to 192.168.1.252. The Plex app is working properly and I am able to access my library, but when I logged in to Plex.tv, it says it can’t find my server and I am not able to make any changes. Not sure if there is a config I need to change for the new IP.
After an IP change of a server, the changes might need a while to propagate.
Most important: stop and restart the Plex server software after a change of network.
Then let it sit running for a few hours.
On the other hand: If the server is still on the same local network, there is no need to give it a different local IP address. Particularly if you disable the old network adapter.