Cannot be added to firebase using polymer <firebase-element> project

I am using polymer to add entries to my firebase. I can successfully log in to the system buy I can not write, I get an error:

'Uncaught TypeError: Cannot read property 'ref' of undefined'.

      

        
        
        
      

    

Has anyone successfully tried adding an entry using the new firebase element?

JS Bin is at http://jsbin.com/nohujoceto/edit?html,console,output