Plex works on cable network but not on fiberoptic network

Trying to move my Windows Plex server from old, cable network to new fiberoptic network. Old network used cable modem and my own router. New uses ISP-supplied fiberoptic router set to bridge mode and connected to similar (newer model) router. Using same computer on both. Works fine on old network but gets “can’t connect securely” message on new network. Have set reserved IP address for server and have port 32400 forwarded to that IP address on new network, but still get error. Can access server on new network using IP address, so I know server is running, but can’t access server from Plex.tv page or any of my devices’ apps. Plex documents the server brings up when I click the “get help” link under the “can’t connect securely” error suggest using features no longer available in Plex. Any help for this?

https://support.plex.tv/articles/206225077-how-to-use-secure-server-connections/

Also, switching routers will definitely cause windows to classify the network connection as “public”. You need to set this back to “private”.

Thank you, Ottto!

Do you have a public facing IP? I recently switched from cable to fiber and I had to pay for a static IP in order to get services like Plex to work. Without it I didn’t get a publicly accessible IP but one that was NAT’d behind their network. Obviously I was unable to port-forward plex (and other services).

Plex has started working!! Thank you both for your responses and suggestions.