Hi @Jonline,
It’s most likely not an issue with the wall stack itself. On September 4, Facebook changed the requirements for these type of apps. You now need to verify the business for which you are trying to display the newsfeeds, then you must submit in the developer site (where you created the app credentials for that client) and get ‘manage_pages’ permission request etc.
Look at the inbox for that ‘app’ and there should be notifications from FB about that.
I just had to do all that for four websites using live FB newsfeeds.
I hope that this helps.
Ricardo