Please make sure the side switch on your device is NOT on the orange position or your device is muted. Turn up the volume with the volume buttons on the side of your device and then restart your device.
If you still do not hear the app instructions, follow these steps and you’ll be able to get it back:
Go to “Settings” > “General” > “Use Side Switch” to and then tap to “Mute”
Open the app you wish to play and switch Side Switch to unmute.
iPhone iOS 7 and up
Swipe from bottom to top, tap the “Lock Orientation” icon on the first row to the far right, and turn it off to fix the sound issue.
iPhone with other iOS
Double tap the home button, swipe from left to right on the bottom. Tap the “Lock Orientation” icon to fix the sound issue.