Thanks for reaching out to us here! I do apologize for any inconvenience that you're experiencing with your Slingbox. If you aren't getting audio from your Slingbox regardless of what device or PC/MAC you are using then it is likely an issue with the cabling or the connections.
This article is a good place to start with troubleshooting the issue you are having:
Hope this helps!
The Sling Moderation Team