I connected my lap top to my hdtv (vizio) with a vga connection along with a sound cable. It worked the first time with no problem and the picture on the tv was almost as high quality as the picture on my lap top. Now when I try to connect my lap top, neither device recognizes the other. The tv's lap top input is blank and says no signal and the lap top does not change or have a window pop up with options (like it did the first time I connected the two devices). Why is this connection no longer working? How can I fix it?