Plugin Registration Tool error : Unhandled Exception: System.ServiceModel.FaultException: MSIS3126: Access denied.

Hi,

I am running Plugin Registratin tool for a  CRM 2011 On-premise Site that uses SSL and Claims based authentication.

I know that I am a deployment admin. And I verified that  the Discovery URL loads in a browser ok.

Do I need to disable Claims based authentication?

Thanks, Peter