Videos clips aren't fully loading

In the past week I've had an issue with most of my video clips not fully loading under the "my media" menu on the left. The still images load fine, and some of the mp4 files load ok. All others show up as an icon that looks like a black piece of paper with white vertical lines on it. When I try to add them to the project, they load as an audio file only. These clips are about 10-20 seconds long. A few show up ok, but most don't. They were shot on a Samsung S23 Ultra, and I'm using Rush Windows 11 on a laptop. I've been using Rush for years, and have never seen this before. I tried moving the files from Dropbox (which is what I've always used in the past) to a local drive. Still nothing. about 20% of the video clips show up normally, the rest are this stupid black paper icon.