The operation for one of the outbound Web services in your service flow lacks both an output message and a fault message. An outbound Web service operation must have either an output message, or a fault message, or both.
Open the .wsdl files in the operations folder of your outbound Web service subproject with the operations editor until you find the operation that lacks both an output message and a fault message. Add an output message or a fault message to that operation, save the operations file, and run the Generate Runtime Code wizard again.