Restoring Thumbnail Previews in macOSRevisionas of Sunday, 25 December 2022 at 00:00 UTC

Got generic-looking icons instead of previews for MP4 files and couldn’t figure out what was going on.

Tried Finder → View → Show View Options → Show icon preview to no avail

Then force quit com.apple.quicklook.ThumbnailsAgent in Activity Monitor and relaunched Finder. All was well.