This is my two cents. I just hooked mine up for our fisrt trip. This is what I found. The TV will need to be set to cable as the source. The white cable jack in my TT has a switch it must be in the cable position and not attenna. Make sure the three wires going to the DVD player are hooked to the Television correctly. Mine had if I recall a Red wire yellow and a white. On my TV it was red to red white to wite and yellow to green on the TV but each one is different.
Hope that helps.
OH one more thing make sure your DVD is set on aux 1 or DVD or whatever the manual suggests. With mine I believe it was AUX 1