Apple Watch is no longer able to control my Music on my phone.

I used to be able to tell Siri on my watch to start playing Music (via my IPhone), even specifying which artist, playlist etc. I used to be able to ask it to play music by artists for which I had no music saved on my watch or phone.

Now it just seems to be unable to start playing any music on my phone. I mainly used this whilst driving to control which music to play.

Any ideas?