You will need to go into the menu and do a channel scan. Until the tv scans through all of the channels and finds them you will not get them. This is also where you would switch between air and cable. If you go through the menu untill you see this you will fix your tv.
I just got this tv, sd-533hd5 and I must be doing something very wrong. I can not get my cable to work with it. I only get about 5 channels. Is there some kind of special programming to get the cable to fully work? I have the cable line running into the back of the tv where it is labeled "cable." Please help where you can, thanks.