We have created a DLL to facilitate access of a 3rd-party WCF Service. This DLL works fine in a Windows Application on our test machines, but when we try to use it in an ASP.NET application on our web server, our web server returns a 505 HTTP version not supported error to the client.

To clarify, the setup is Client->Server->WCF Service. Using Fiddler, I can tell that our server is not making requests to the WCF Service. The calls are wrapped in a try/catch block, but no Exception occurs. Instead, as soon as the call to the service is attempted, our server returns a 505 error to the client and terminates execution.

We are using clientCertificate authentication over HTTPS with serviceCertificate certificateValidationMode set to "None".

Thanks