Getting your Plex server to use UPnP (Universal Plug and Play) will increase speeds, along with allowing it to run on more clients. For example, one Smart TV’s Plex app did not work until UPnP was enabled on the server’s home network.

Identify if you have the problem

These are all symptoms of not using UPnP:

1. While the error message of “<Computer> is offline or unreachable” is vague, if other clients are working, this might solve your problem.
2. If you get “Indirect Connection” warning dialogs, then this will fix your problem.
3. To determine if UPnP is on, check in your Plex Server Settings if Remote Access is enabled. Follow this good Plex support article.

Enabling UPnP

Enable UPnP on your server.

1. Windows instructions

Port Forward 32400 on your to your Plex Media Server computer.

• Plex support article.

Refresh your Plex Server Settings and the red globe should become a green globe!

Sources

• https://support.plex.tv/hc/en-us/articles/200484543-Connecting-a-Server
• https://support.plex.tv/hc/en-us/articles/200931138-Troubleshooting-Remote-Access
• http://www.thewindowsclub.com/enable-disable-network-discovery-windows