Firewall will not be hosted but OK locally

I host my box on wayne-o / xubuntu-md - the file is on my Dropbox share.

Now - if I add this file locally with vagrant box add st package.box

I see the window is being added as st to my list of local fields.

Now - if I try to use a loaded box using

config.vm.box = "wayne-o/xubuntu-md"

      

        
        
        
      

    

I am getting the following error:

The box failed to unpackage properly. Please verify that the box
file you're trying to add is not corrupted and try again. The
output from attempting to unpackage (if any):

bsdtar: Error opening archive: Unrecognized archive format

      

        
        
        
      

    

Has anyone experienced this?