What does this error mean, and how do I fix it?

GoDaddy and other domain hosts do not allow you to change the root domain configuration for a domain, therefore the base domain of your website must redirect to the www version. You can find the instructions to set up an external domain here. 

Since some hosts do not allow this configuration, you may receive an error in the app saying that it is configured incorrectly. If you're able to view your website online using the external GoDaddy domain, there is no need to worry and you can simply ignore the error!