Error on ROKU when attempting to stream from PLEX



I am looking for support in resolving a random error that just started popping up on my ROKU when attempting to stream a movie from my library through PLEX App on ROKU.
the error is " We're unable to play this video. Make sure the server is running and has access to this video".

i have all my movies on NAS storage on the network. we've always watched movies on ROKU through plex under this same setup for over 3 years. i want to say that this issue started happening when PLEX server was updated.
i have tried several things, including downloading an older version of PLEX server on my laptop and trying to stream from that and is still give me the same error.

please let me know if you have come across such error and how it was resolved.
Many Thanks,