Hi,
do you get more details in ther server.log of vCO?
(You can temporarily set the loglevel to debug...)
What exact version of the SOAP Plugin do you use?
Usually such an error points to an wrong/not-standard-conform WSDL file.
Do you get a proper wsdl response when calling the wsdl uri in a browser?
Since you use https: Have you registered the SSL certificate of the endpoint prior to adding the host?
Cheers,
Joerg