Installed Linux 20...Installed Plex Server... Can Not connect to Plex Server

Hi
I installed Linux Mint 20. Then I installed Plex Server. Now when I try to connect to the Plex Server, I get a message that the connection is not secure and will not connect. In settings I have Secure Connection set to preferred. This happens across all players. Windows app, Roku App, and Apple TV app. All worked fine before. When I run the server from the Linux Mint computer, the server works fine. Any suggestions would be appreciated.
Thanks
Doug

Firewall issue in Mint?

Thank You…
You were correct… I closed the firewall and that solved my problem
Thanks again
Doug

You’re welcome. Glad it’s working!