What is the music source you’re playing? How is it being played?

For instance, if you’re using Bluetooth to send the audio signal from your phone to the speaker, moving to another room may block the signal from from your phone going through the wall to reach the speaker. 

Your mobile device does not communicate with your speaker directly (except during setup), it only ever communicates with your wifi router.

Unless you are using Bluetooth however, when Bruce’s response is the one to take.