Sorry, I’m not familiar with Facebook apps and how they work. I didn’t notice there was a new settings page for this plugin, so thanks for pointing that out. When I go there I see this instruction: “Create a new app and paste App Id here”
Unfortunately I don’t know exactly how to “create a new app.”
For future reference, you might want to amend your plugin description which says all a user has to do is activate the plugin and it just works. And maybe mention this step. Believe it or not, there are plenty of us out there who haven’t worked directly with Facebook apps. ??