Video Clips Downloading blank

New to Envato, found video clips that suited a project but a few days into subscribing the video clips are downloading but the playback is just dark. No footage whatsoever. Can anyone shed any light on why?

Have you tried opening these video-files in any video-editor?
Some video-files are not shown in preview, you can see previews only by opening them in any program.
Is it installed/updated QuickTime codec on your PC?