Thanks for using our answers forum! I'm sorry to hear that you're having this audio issue with your Slingbox PRO HD. It sounds like you have already gone through some troubleshooting steps here. Have you tried another set of audio cables?
Here is an article from our support site with some additional steps that you can try regarding this issue:
Hope this helps!
The Sling Moderation Team
Thanks for the prompt reply. I have tried to use different cables between the Slingbox and cable box with the same result. Which is that, I have video and sound on my TV that is connected to the passthrough, but not sound is being sent to any device connecting via the Slingbox over the home network or Internet.
Do you have any other recomendations?