If in case all content version is not visible then need to do below additional settings:
- Go to Setup and Search Permission Sets (choose an existing or create a new one).
- Click on the App Permission then Content.
- Click on the Query All Files.
- Assign the newly created Permission set to the User who's having a Mass File Download license.
Note: Query All Files is not enabled by default for the admin user but you can at least enable it in a Profile/Permissions Set.