sorry it took so long to get back to you, we were invaded by grandkids and they have just left.
What version of Piper are you running?
Have you updated the pi?
sudo apt-get update && sudo apt-get upgrade -y
Go to the Menu->Preferences->Audio Device Settings and see if you see this:
Press the ‘Select Controls’ and you should see this:
I then check off the PCM box and hit 'Close:
You should now see the volume control:
Try adjusting this and see if you have sound