I would try to reseat all the connectors on the sound board and mother board. Pin-Bot has sound on the main mother board as well as the sound board. Make sure all chips a seated too. Mine did the same thing when I first got it, but after going through and reseating everything it worked again. Also check and make sure the speaker isn't blown or came unconnected. I had that problem too.

Only problem I have now is the voice goes out after about 30 minutes. I'm assuming because of a bad capacitor that slowly dissipates which is why the voice slowly fades away but comes back after it's turned off and on again.