Plex Media Server version?
Plex Media Server platform? (Windows/Linux/etc)
Plex client versions?
Version info available via Authorized Devices: https://app.plex.tv/desktop/#!/settings/devices/all
There have been many recent reports of problems with the Android TV and Android mobile clients.
Updating to the current server and client releases, when possible, has resolved the problems for many users.
Also, see this thread. Many users reporting the same problem:
An error occurred while attempting to play this video check the connection and try again
