AIF Outbound in ax2012

Hello Friends,

   I want to export the sales invoice in xml and save in one folder (i.e Ounbound process in AX2012).

I am go through this link - http://dynamics-ax-developer.blogspot.in/2012/09/ax-2012-export-data-with-outbound-ports.html

but i got an error in queue Manager - Status - Error  and  Error Message - "No valid document identified from the entity key"

Thanks,

Darshana