Lightroom Classic Video Issue

[lydias99557819]

I am struggling to figure this issue out. PLEASE HELP!!!!!!!!!

I uploaded all of my video clips into Lightroom Classic. Once I trimmed them, etc, I put them into the Slideshow module. I added music, adjusted things, etc, but the one thing I could not change was that my video had a HUGE, THICK, black border around it. I've exported it many times thinking it would go away, but instead my video is a small square inside a huge black frame. I do NOT KNOW HOW TO FIX THIS! I selected "Crop to Fill" in my templates and it showed up as full screen in my preview screen, but once I hit preview or play on the slideshow the videos went back to being in a large colored frame? Attached is an image. Please help!