QuickTime No Longer Opens MP4 files

[Eric Idle]

I have a very large collection of MP4 files that I used to watch with QuickTime. I have not watched any in awhile so am not sure when this fialure occurred. Today I upgraded to 12.6.5 which might have something to do with it.

When I click on a movie, Quick Time starts up but does not do anything. No error messages appear. Nothing happens and eventually QT just closes itself.

I'm at a loss at what to do next about this. Advice?

 

[Eric Idle]

Well apparently it took a good 3 minutes or more to open up this movie so now it works. These are short 2-3 minute long files so I have no idea why such a long time was required to open it. Maybe the update to 12.6.5 has caused some background work to slow things down.