No channels

I have a tivo premier 4, recently it stopped receiving channels all together. After talking to Tivo( they said it was the cable card) I went to comcast and replaced the cable card. Several attempts to pair the card were unsuccessful, status on the card is inactive. Initially I thought it was just Comcast usual incompetence but when we 3 way conferenced with tivo and comcast, we discovered that I wasn't receiving any signal strength at all , the tivo rep said I should get some signal even without a cable card installed. To trouble shoot I moved a cable box to the room and it worked fine with the tv, so the cable is fine. Has anyone had this issue?

Jojo