Cannot access Plex on port 32400

I have Plex Media Server on my Windows 10 PC. It was working fine until a power outage 2 days ago but now it is not allowing Plex connections from outside my private local network (the router is working for other internet access, such as this page)

Plex is running on port 32400. I'm trying the Plex troubleshooting guide https://support.plex.tv/articles/200931138-troubleshooting-remote-access/ which suggests trying port forwarding, but from http://www.routerlogin.net/adv_index.htm it fails,

 

telling me my port range is in use.

 

 

 

 

 

 

 

 

I have firmware V1.1.0.80_1.0.1

I am running WebRoot Secure Anywhere on the PC and have Windows Firewall turned off since WebRoot provides a firewall. The Plex Media Server .exe is listed in WebRoot allowed applications, and it is running but Plex reports for Remote Access:

Not available outside your network

Your server is signed in to Plex, but is not reachable from outside your network. Learn more

 

http://whatismyip.host/ reports my IP v4 but CanYouSeeMe.org shows

 

Error: I could not see your service on xxx.xxx.xxx.xxx on port (32400)