Server Version#: 1.23.6.4881
Player Version#: 8.20.1.26670
I have a series in my TV library that works fine with Plex Media Player on my laptop and on my Android Phone but won’t play on the Android TV device plugged into my smart TV. I’ve tried emptying the trash, cleaning bundles and optimizing the database on Plex, as well as clearing the cache on the Android TV device and restarting the device. I’ve also tried casting it from my Android phone to the Android TV device: I get the same error if I cast to Plex but it works if I cast to the device. I haven’t watched everything on my Plex server but, so far, this is the only series I’m having trouble with. TIA for any help 
This is what happens when I try to play an episode:
An error occurred while attempting to play this video. Please check your connection and try again.
Plex ‘Get Info’ for one of the files:
Size: 2.63 GB . 3.8 Mbps . MKV
Video: 960x720 . 23.76 fps . 3.5 Mbps . H264 4.1 High
Audio 1: English . AC3 . mono . 320 kbps . 48000 kHz