See my comment above, it could be a browser issue?

I found that this was a problem for me too. It ended up being a codec or container format (maybe MKV container?) that was not supported in my browser (Firefox). I dug into it and realised that the latest version of FF which I could get if I used the Mozilla repository, completely solved the problem.

Ditched this crapware for Jellyfin several years ago. Glad I did. It’s been great.

Nice