I was recently making a video in sony vegas pro 16 and I've been chroma keying a lot. I went to put in a greenscreen, there was a green box in the center which was annoying but I was able to deal with it. Now, whenever I try to chroma key, absolutely no effect changes. I can play around with the colors and nothing happens to the video.
lol, you are a lucky one to have Vegas Pro 16 when only version 13 is available for everyone else, lol
Any way make sure "Split Screen View" is not enabled, the button is located just above your Preview window.