our blue ray player wont work?

[DennyWillard]

my family just bought a blu-ray player, an hdmi cable and a new tv. they are all the same brand (vizio). anyway when we put a dvd (not blueray) into the blu-ray player and hit play, all we get on our tv is a green screen, yet we can hear the movie playing. please help us figure out how to make it work.(the blue-ray player is called "vizio blue-ray player vb120")