Hi. I have the same issue my wirering is correct and I get an image and sound just fine but when setting up sling box 500. It can't find scientific atlanta 4250hdc. And so when it promps you to test with remote and view the image to the right mine doesn't change and in the six or eight Small squares that should show different remote commands it doesn't show anything just a small dashed line in the little square.
So im guessing the sling box can't find the popper setting for my cable box and can't generate the correct remote functions. If this makes may sense. Thanx in advance for your help.
Ps. My cable provider is cox communications.