QuickTimePlayer не работает

Launching the QuickTime Player app will bring up an Open… dialog box, where you may select a media file. It may point to an empty folder on your iCloud drive initially, but you can navigate your local disk, e.g. using the side bar. The app will remember the last used location. If you do not wish to open any media file at that time, then click Cancel. (Note that there are no other windows for the app, and clicking the desktop background will quietly quit the app if there are no documents open in the app.) Find various app functions in the menu bar.

This is how the programmers intended it to behave.

QuickTime Player user guide for Mac - Apple Support

What doesn’t work specifically? What were you trying to do with QuickTime Player?