The most likely reason why you are still running into this error is because you may be trying to access our API through your personal computer or basically any other source than you gave in your server url (stored with the app).
We only allow API calls from the server that can be reached with that URL.

So my suggestion is to upload the script (or if not present yet, create one and use something like curl to get the source code (json return)) to the server you supplied and access that script so it will be run.

Tell me if this fixes your issue, or feel free to pm me and give me your skype id, so we can clear this out in a real time chat with the option to share your screen.

Regards,
/JoNny