Your operation did not fail.

Your backend service is saying that the response type it is returning is not provided in the Accept HTTP header in your Client request.

Ref: http://en.wikipedia.org/wiki/List_of_HTTP_header_fields

1. Find out the response (content type) returned by Service.
2. Provide this (content type) in your request Accept header.

http://en.wikipedia.org/wiki/HTTP_status_code -> 406