The restful endopoint requires authentication with a valid Denodo user, "admin" for instance.
If you need to publish a web service with no authentication, right click on a view, select New > Data Service > REST Web Service, and then in the settings tab set Authentication to "None". You can also set up other authentication options.
Once you click OK, click on "deploy" to have it available in the embedded web container. It will be available in the context path displayed in the web services table. For example, if the context path is "server/tutorial/mywebservice", it will be available in http://localhost:9090/server/tutorial/mywebservice