I also verified that the desktop Plex application was able to open the test file when disconnected from the internet, but the Android TV Plex application was not.
In addition, while I was disconnected, I was unable to retrieve the log files, since the uri was online as well.
I’m having this issue with my new Mi TV 4S 43" with latest plex server (1.20.1.3252) and plex client. The video always plays ok but the subtitles never shows on.