I was able to open .mp4 files from Quicktime, iMovie and also to play from the Fider preview. Once I upgrade to Catalina, I can't play the .mp4. The files open, but and play, but doesn't show video, just black screen like is not codified for play. I can see the timeline progress playing, but no the video. I did the restart Safe Mode, check the Pro Video Format. Help Please!!