Turns out I was incorrect about the Insignia. It is a 26" screen and the model number is NS-ldvd-26Q-10A. The Panasonic is a TH-42PXG0510. It is a plasma TV. Could this be the issue? Mediacom is my cable provider and they have not been near either one of these TVs. The cable outlets in these rooms were set up twenty years ago by a different company and have always worked just fine. I scanned for both antenna and cable channels several times and go zero results. I moved this TV into another bedroom with the same set up and it didn't work there either, although the TV that it replaced worked fine. The TV works fine as a monitor for my son's Playstation, so I know it works.