Digital Television - XFinity

I just installed a Magnavox MDR868 DVR in my home theater system. Running my Comcast cable TV signal directly into the DVR, I am unable to get the DVR to recognize cable TV channels. It scans the cable tells me it found over 500 channels and then skips almost all of them because they are not usable. How do I solve this issue?

This question, "Digital Television," is about XFinity-Comcast TV television equipment.

For other news regarding Digital Television, and XFinity - Comcast television equipment, see our recommended stories below.