There can be several reasons why Spotify does not start. Try these options to solve the issue:
1. Push and hold the control knob for 10 seconds to restart the headphones.
2. Check if there are any new updates of Spotify to install on your connected audio device.
3. Make sure that your M-button is configured to start Spotify. You can customize the M-button behavior in the Marshall Bluetooth app.
Perform a factory reset to restore the headphones to their original settings.