Okay then, I'd recommend creating a support case for that if you haven't already.
Generally that message means that it could get the credentials for your database from the server via an http request to a specific site. You may be able to find some errors in your IIS log that would point you to the right place. hopefully it's as easy as making some IIS configuration changes but like I said before you'll want to chat with our support team when you have a chance.