Remote Access keeps coming "Off"

Use a service like canyouseeme.org to check from the outside if a port is reachable.

Not with these settings above. You are instructing Plex to propagate port 32400 for outside access. However, your router is by default using automatic port forwarding, which picks a random port number.
Either clear the checkmark before “Manually specify port”,
or define a manual port forwarding in the settings of the new router (recommended).