Facebook ‘Use Strict Mode for Redirect URIs’ Help!

Facebook, within the last week or so has changed its ‘Use Strict Mode for Redirect URIs’ to permanently on which means that , as far as I understand it, any entry in ‘Valid OAuth Redirect URIs’ has to be an exact match to that in the website. This is where I am totally confused because try as I may I cannot get it to work.
Can anyone offer a constructive answer or any clear hints as to what entries should be applied to ‘Valid OAuth Redirect URIs’ and/or how I might get it to work.
I am getting the error:
‘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 sub-domains of your app to the App Domains field in your app settings.’, which I believe is a result of an incorrect ‘Valid OAuth Redirect URIs’ entry.
Thank you