Hello, have you checked the sound level of your audio source when you are creating the screen and have you checked that you have chosen the correct source in your design view?
Also worth checking is the volume control/mute setting on the screen Windows set-up itself.
There are quite a few different levels to check so have a good look about in the design view where your audio source originates, also check that the audio file has appeared in the D: drive of the screen after you have published it [just to make sure it is actually available to the client].
Let me know if you still cannot get it to work and I will try and help further.
EricL