At the risk over having overlooked something. Music won't play anymore giving the "not available" error when using the latest version. Previous version was fine.
Every time a new version is released I release my current version to *_old and give the new version the proper name (to start as a daemon).
New version won't play music with mentioned error, old one is fine. (also stopping, starting, etc)
The experimental music code was removed from Plexconnect around the time of UI integration. Baa found that the implementation was too flakey and decided to remove it until a better approach can be found. So, to sum it up, music is not currently supported.
No matter how, what or why, I am very happy with the app and leave the wise decisions up to you. I'm just happy not having to investigate something that is not an error but on purpose.
Not using music anyway, but it not working annoys the hell out of me. So I'm happy with the explanation.