There is a known issue between older versions of Plex Media Server (1.18.x, 1.19.x, etc) and the current Android & Android TV apps.
Updating to a current Plex Media Server release fixes the problem.
If you cannot update PMS, the workaround is to disable secure communications.
You can verify you are experiencing the same problem by looking for certificate errors in the Android / Android TV app log file. Look for lines containing: [FFmpeg] [ERROR] [tls @ 0xc597c7e0] Peer certificate failed verification
There is no additional information at this time regarding a fix for the problem.
