Actually, we did debug this and found that your server is returning a 403 forbidden message when we attempt to connect from our API. Our developers asserted that there could be some rule set up on your web server that prohibits connections like this. From the browser, the connection is allowed. Perhaps you can investigate how your web server is configured with this regard.
We have made a change on our side to ignore this error in this case. It will be released in December.
Thanks,
Mike