Check to see if the clock has a lever to turn the music on and off. The lever may be on the bottom of the clock by the pendulum or on the side of the clock.  The lever on the bottom of the clock is a push n pull lever. If the lever is on the side of the clock you can slide the lever up and down. Try the lever in both positions to see if the music starts playing.  

The music box may be defective.  You would need to send the clock to us so a technician could solve the problem.