me biztalk and commerce gateway

i am trying to set up and configure the commerce gateway for MBS navison 4.0 thye system displays me this message:
\”no connexion established with biztalk server\”
i ll describe my configuartaion
i have installed biz server 2004 on sql server 2000 sp4
i have installed commerce gateway request server 4.0 on the same machine and started the service on local system
i have installed navison client database server and nas on the same machine as biz and commerce gateway i created a nas service for the compagny and i started it
i have configured the business partner and when i am trying to send a purchase order to partner i receive the message written below.
pls help