Issues when calling KC API with SoapUI

I started using SoapUI to issue requests to KC APIs. Most of requests fail with "Error: Invalid context". in case of GetReferencesByIshLngRef that is available under Reports20 class I use psLngRefs as it is defined in language configurations. Any help is appreciated.

Also, what is not clear is how to handle authentication. We are using ADFS authentication for Knowledge Center. In such case I don't believe we should use login function.