Black box in between clips

I will not tolerate this. I need to finish something by tomorrow and but something I have paid just so much money for is wasting my time. I spent hours editing a presentation thinking, "hey, this is Adobe, they're professional", but apparently not! I know there is no way to finish this now because an issue has occured. I am trying to overlay a video over another video, super simple. Everything is glitching and lagging and not working. I was also expecting more features in the rush version but no. I need to connect two videos but there's a grayish-blackish block in the middle, the color of the background and I can't find a way to connect the videos together. This is a long video and I've figured out that if I drag the next clip to the other side of the block, it might work, but I can't even drag multiple video easily with this software. Note this is a very expensive and brand new laptop as well, the 2019 15" Macbook Pro with Touch Bar, so that shouldn't be the issue. This isn't even a hardcore project, easily could be done with iMovie but I don't have time to search through to find all my clips again to try again there. I assumed maybe Adobe would have tried something better and different then iMovie but from now on I'll resort to there. I'm sure this is a mistake but don't charge customers so much for service like this. Also I noticed there's no chat system?