If you are debugging an issue with getting properties from a JSON response, I would recommend printing your entire JSON response on a Label first. If you have an error with this, you need to revise your Web API call. If you can successfully print the entire JSON response, then you need to make sure you are getting the correct properties of your response.
You can see an example of this narrowing down of a response here: Reverse Geocoding App - Get Location from Latitude/Longitude