Thanks for the response. It was actually just something stupid on my end: I didn't have the dropbox link set up in a public folder.
I'm having another error now though. When I load up our game package in cocoon a lot of the assets are just showing up as white squares or flickering in and out. Some of the assets are fine but certain ones are having serious problems. Previous builds haven't had an issue so I'm just wondering if there's a setting somewhere that Cocoon doesn't like.