Failed to instantiate WebClient class - SOAP out bound adapter

We are trying to call a SOAP web-service from Ensemble, following the documentation here: Creating an Ensemble Web Client | Creating SOAP Services and Web Clients with Ensemble | Caché & Ensemble 2018.1.4 – 2018.1.8 (intersystems.com)

While the version of Studio on our system doesn't display exactly the same options as described when using the SOAP Wizard, it did create a set of classes that look to be covering the correct bases - a set of Request and Response classes relating to the methods presented by the web-service, as discovered via the WSDL, and an Operation class and a few (9) SOAP client classes.

Created a production, with a Business Process component that is building a request and passing it to an Operation utilising the operation class produced by the wizard. The request is being produced OK - can see message passing from the business process to the operation OK, and its content looks good.

However, when the production starts up (ie before any request is being built or any attempt to contact the web-service) we get: "Error: Failed to instantiate WebClient class". What are we doing wrong? Some screen grabs below: