Domain Mapping & Ultimate Facebook

So I mapped a domain to my multi-site store

Since then FB login says:
Can't Load URL: The domain of this URL isn't included in the app's domains. To be able to load this URL, add all domains and subdomains of your app to the App Domains field in your app settings.

I have gone to the app in FB and added in the App Domains field but I am still getting the same message.