It's possible that when you go to the Clip info to download the original media for a clip, you see a little x next to 'Original media' as seen in the screenshot below.

This means that you can't start a download, because the original media is not on Flow. This could be for several reasons:
- You've uploaded the media through Edge, in which case the original media was never on Flow.
- The media has been purged.
- In case you are using cloud resources: there are insufficient resources.