Nike Apple Watch series 5/streaming music without my iPhone

I just purchased this watch with cellular so that I could listen to Spotify while I'm training without my iPhone. I have my Powerbeats pro paired with my watch and the watch paired with my iPhone, I can stream Spotify through my watch to the headphones when my phone is near. As soon as I get 50 feet from home, where I left my phone, the music turn off. Can you please tell me how to use Spotify on my watch without my iPhone, and stream through my Powerbeats pro headphones?