Although other apps may have sound, it is possible that your iPad is muted. To turn on the sound, take the following steps:

1. Check the "Mute toggle" on the right side of the iPad, just above the volume rocker. If you see the color orange, the device is muted.
2. Open the Control Center by swiping down from the top right corner
3. Check the Volume (speaker) control - a slash through the icon will indicate sound is muted
4. Swipe up on the Volume control slider to unmute and raise the volume on your iPad

For further assistance with sound control on iOS devices, please visit the Apple support site.