I used to be able to preview video, photos and audio in Finder without opening. Now it just shows file information.

I used to be able to click on the space bar for audio, video or graphics, and it would play the track/ play the video/ show the photos WITHOUT loading into iTunes/ quicktime player/ etc or any other programme in preview mode. Now it just comes up with some kind of information about the audio/ graphic/ video, but doesn't play it.

Someone had a chat about icons, but it's not that. Someone else had a chat about signing out of iCloud and signing in again, but that hasn't helped. And someone else said the files are corrupted by I ran scan disk and there's no corruption. It doesn't seem to be linked to an upgrade or anything, just quite at random.

Any help? Thanks!