One of the steps of 'Add a REST host' workflow is to select authentication type. Default is NONE (no authentication); you should select various authentication types like Basic, Digest, OAuth, etc.
Did you configure some authentication there, or left NONE?
Another question - what's this :80 at the end of the operation?
Also, what happens if you try to call operations that require authentication but are not PUT but GET or POST? Do you get the same error?