Hello and welcome to JUSTANSWER.com
I think i understand WHY its not working.....but i need to first understand the EXACT cabling that is being used, and WHERE each connects. This is important, if you are using DUPLICATE connections it can be confusing to the PC and the slingbox as to which to use, and will auto-disable if detectable.
So, please explain IN DETAIL how each cable is connected, the type of cable, and what is connected at each end.
If it all is normal, then we will continue to troubleshoot other settings.