Well, check the UI that it didn't work (remember to reload), see https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html for explanation of code 204 :)
Also, are all the requirements met? ("Makes the view with the given id the default view for the app. The view must be of type "saved" and must be active. In addition the user most have right to update the app")
So, the view must be saved and active, and user must have right to update the app - app authentication won't work.