The sound sometimes does not come due to changes in iPad settings. There is no fault in the app. You can confirm the same with headphones. Follow the below steps to enable sound on iPad.
a) Go to Settings > General Tab. Change the side switch to control Muting.
b) Mute and Unmute with the side switch (on the side of your iPad).
c) Test the app and check if the sound is audible now.
d) Increase the volume while the app is running.
e) If ok now, go back to Settings and make the side switch to control screen orientation again
f) Go back to the app and check if sound is still there.
Email us if you still face any problem.

The sound sometimes does not come due to changes in iPhone settings. There is no fault in the app. Restart your iPhone. Then mute-unmute with the side switch. Now you start the app and increase the volume while app is playing. Email us if you still face any problem.You can watch the video here.

The sound sometimes does not come due to changes in settings in the iPad Air 2. There is no fault in the app. You can confirm the same with headphones. Follow the below steps to enable sound on iPad Air 2.
a) Swipe up from the bottom of the screen to open the Control Center.
b) You will see a Mute-unmute button (the Bell icon). Tap on it to Unmute it.
c) Test the app and check if the sound is audible now.
d) Increase the volume while the app is running.
e) Sound should be heard now.
Email us if you still face any problem.