New to Jellyfin - can't play audio or video

[BarleyBreathing]

I just set up Jellyfin - my first media server. I am able to connect my phone and laptop to the server, but I am unable to play any music or video. Videos look like they are going to start but don't, and I get the "jellyfin playback failed due to a server error" error when I try to play any audio (mp3 or flac) file. Hardware acceleration is disabled by default. Given that this is all new to me, I'm not sure what to check. 
Here is a link to a log.

https://pastebin.com/embed_js/i2vksY59

Thanks