When I upgraded to the new version of LR in my catalog none of the videos (.mov, .mp4) work. They all have exclamation points on them and when I try to play one I get the error "There was an error working with the video". They don't have Preview icons either. They all worked just fine before the "upgrade".
When I try to import any video I get the error "There is a problem with the video file (1)"
On the hard drive all the videos are fine, and all play properly in Quicktime, Premiere and After Effects. They have the proper permissions (read/write)
I tried creating a new catalog - no change. I tried creating a new user on my system - no change.
I uninstalled and re-installed LR. No change.
I then used "AdobeCreativeCloudCleanerTool" and all the instructions on its page to remove Creative Cloud from my system, and then did a fresh install. No change.
The files are fine. Every other program can read them just fine except Lightroom. Any idea what else I could try?