This issue is an issue with the way iOS handles sounds and specific to iOS devices.
The issue generally occurs when there's another sound that plays while you're in the game, such as a notification, which overrides the sounds in the game, causing them to shut off. To fix this, you can try using silent notifications on your iPad.
This link can help if you don't know how to do this: https://support.apple.com/guide/ipad/change-notification-settings-ipad870e28f5/ipados
If this doesn't work we recommend contacting the Apple support team at the link here: https://www.apple.com/support/