QuickTime No Longer Plays Videos in macOS Big Sur.

Over the weekend, I updated my iMac (Retina 5K, 27-inch, 2017 model) to macOS Big Sur (v. 11.2.3).

The computer seemed to be working well, overall. But, just now I started to notice that QuickTime Player (v. 10.5) no longer plays my videos. These include not only newly-created videos, but existing ones that always played in QuickTime with no issues. The app literally will not play any videos at all. Most of these videos are .mp4 files. I can open the files, but when I click the play button, the app does not respond. I can fast forward, fast reverse and move the time slider without problem. But clicking play just doesn’t work.

Also, it used to be that I could preview the videos in the Finder by clicking the Play icon on the video file’s thumbnail. But, they no longer play that way, either.

I notice many people on these boards who have upgraded to macOS Big Sur have complained about playback issues in QuickTime. So I am assuming Apple needs to correct the bugs in QuickTime and/or Big Sur and issue new updates. I hope Apple does that as quickly as possible.

In the meantime, is there something simple I can do that has been proven to remedy this situation?