YES!!! I am also having this issue, and can't for the life of me figure out why.
I have been using VPT for a year now, and never had the issue. Today, I opened VPT to work on a project, and whilst changing the source for one of my layers, everything just went blank. I tried to select video inputs, but nothing was displaying even in the monitor preview section. It had been fine when I first launched it. I tried closing and relaunching a few times but the issue persisted. Eventually, I uninstalled the whole file and re-installed it via the download again. I launched this brand new version of VPT I had just installed and nope - nothing. It is supposed to run the test clips when it first launches, but even they aren't displaying. I have linked the video folder in by dropping it in, I have selected and deselected monitor display, I have clicked the little display boxes on and off. Nothing. All I can create are solids - as soon as I try to load in outside media, it just will not display.
I'm on a PC running Windows 10. The strangest part in all this to me is that it was working fine, and then it suddenly wasn't, and there seems to be no reason why.
pls halp