you probably have an early model S+ machine, make sure the volume pot is not turned off,put it in the center position, you will see a tiny piece of plastic on the wheel as you turn it, this is the center position, the white test button is located on the outside of that housing about in the middle, press it until you see a 50 in the winner paid window, the spin button should be lit, press it , it will make an audio tone, each time you turn the jackpot reset key it will change the number and the tone, this will test all the sounds this machine will make.
make sure you dip switches are set accordingly 1234 on 5678 off.
Jim