Is the file a single image, or more than that?
Try this:
- Navigate to where the file is.
- Click on it ONE time to select it
- Type "command-c" (copy)
- Click on the desktop (just on the desktop, not on any file)
- Type "command-v" (paste)
- A copy of the original should now appear on the desktop
- Does it?
If the file can be copied to the desktop (as you just did), can you now "grab it and drop it" onto the icon for the external Element drive?
If this doesn't work, do you get any kind of an error message at all?
If so, what does it say?