I've been using Vegas Pro 15 since December 2018. I've been using the picture in picture function for at least the past two years. I recently built a new computer, downloaded, then installed Vegas. I've gotten most of the way through editing a video and tried using the picture in picture mode and the area around the video to be overlayed is completely black instead of showing the video underneath it. (See attached sample screenshot). I rendered the below sample just to be sure it wasn't just like that in the preview, but it's also black after being rendered.
I'm not sure if it's a setting I tweaked so long ago on the old computer that I've forgotten, or if this version of Vegas just isn't compatible with my new computer. Any help would be much appreciated.