If you have no sound on Rhythm Cat, Treble Cat or Bass Cat, you may have accidentally muted your device. Even if you’re still getting sound through headphones or core apps such as Youtube.
On Newer Devices: (that have no side switch next to the volume buttons)
– Access the ‘control centre’ by swiping up from the bottom of the home screen – you should then be able to unmute your device.
Here’s a support link from Apple that provides more details.
On Older Devices:
Go to Settings – General – under ‘Use Side Switch’ make sure ‘Mute’ is selected and not ‘Lock Rotation’
If that doesn’t do the trick – there are also a few more steps outlined here too.