I can not get the cable to come on with the panasonic TV combo the vcr and dvd player works but when I try to watch cable its all blue screen

I can not get the cable to come on with the panasonic TV combo the vcr and dvd player works but when I try to watch cable its all blue screen

Bypass the Combo for a test, to verify cable is good to that point.
Blue screen cand be no signal.
Try another source/input.