Your app keeps crashing! It keeps shutting down! It plays and then shuts down! Do something about it already! Why do I have to pay money?! I can't listen to my favorite music!!!

I have the same problem. To get around it, make sure the deezer app is not running. Then say “hey Siri, play music on deezer”. Siri will then ask permission to link with deezer. Say “yes”, and your music should start playing. For some reason deezer won’t work with some Bluetooth devices with the app loaded. This makes it impossible to select music via the app (since it’s not loaded) but at least you can get some tunes with Siri in control.