When NB16 connected to phones - Spotify doesn't allow the continuus song playback. After each song, the user has to press play on the app.
Therea are two solutions you can choose.
Forget device, then kill the app and launch it again.
If you are connected via Bluetooth, go on the device you're connected to and select 'Forget Device', reconnect it and click play (also having restarted the app).
Similar applies for the USB connection. While connected, double click and swipe up and close the app (for iOS) and re-open the app to being playing.