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Cannot setup Fiddler as HostServer Proxy on K2 Five 5.3 due to Configuration Service

This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice. This article is not considered official documentation for K2 software and is provided "as is" with no warranties.


Starting K2 Five 5.3, if you are trying to use Fiddler as proxy with K2HostServer to capture server side calls, the K2 Server service won't start and will display an error as below:

"ErrorMessage","SourceCode.Hosting.Server.Runtime.HostLoadBalancedServerManager.Poll","0 System.Exception: Error (401) Unauthorized.

   at SourceCode.Configuration.Client.Extensions.RestSharpExtensions.EnsureSuccess[T](IRestResponse`1 response)

   at SourceCode.Configuration.Client.ConfigurationClient.GetServices()

   at SourceCode.Hosting.Server.Runtime.HostLoadBalancedServerManager.Poll()"


The K2 HostServer fails to start.

Troubleshooting Steps


  • Export the “Environment Owner” certificate as ClientCertificate.cer (the file must be named as ClientCertificate.cer)


      • No need to export the private key
      • Place the ClientCertificate.cer under %USERPROFILE%\My Documents\Fiddler2\ClientCertificate.cer
      • Restart Fiddler
      • Start the K2 Server.

K2 Configuration Service uses client certificate authentication and Fiddler does not know which certificate to present to it.