Really sorry to hear you're having trouble with the sound on your Sky Apps.
As simple as this sounds, could you check to make sure you haven't got the sound switch set to silent on the device. This can sometimes affect the volume on some apps as well as the tones for notifications etc.
Another tip is to go to settings > General > Use side switch to: tick lock rotation If this is on and your volume is turned up, try deleting the app, re starting the device and then re-installing the app to see if this helps.
Let me know if that helps!
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