If you are having issues calling your API, make sure you are passing through your API key to your API call.
To use RSS effectively your API property names must be: title, description, author, category, pubDate or Comments. Else your data will show up as empty in your results. Additionally your API needs to have only one collection. You can adjust your API to be RSS compatible by editing your API.
The HTTP header in the RSS response returns with an
application/xml content type and conforms to the standard RSS 2.0 specification.