I'm using a Nokia Lumia 635 with Windows Phone 8.1.
The app doesn't work. Whenever I try to play a playlist or whatever, it either plays like one second of the song and then goes silent, or it doesn't do anything at all.
Also, navigating the menus is a constant stream of "resuming" prompts, it struggles loading playlists (it says it's impossible to load the playlist and to check my connection - the connection is fine), it crashes. It's just a general mess. 
The app is updated. I reinstalled it a billion times. I tried updating to Windows 10 Mobile. It still didn't work. I wiped the phone and did a clean reinstall of WP 8.1. Nope.
I'm on OS version 8.10.14234.375 and Lumia Denim 3.15.3.54, all in the Italian version if that's any use.

Oh and just to make it clear, this is not a case of "it worked just fine until it didn't", it never worked.
This is making me very sad 😞