How to remove "Please, enter correct Facebook API settings" and connect to facebook?

I had once connected Facebook with my site using Facebook API settings in Ultimate Facebook Plugin. Then i deleted that Facebook app and created new one and fill up new App ID / API key and secret key and try to connect to face book. But it doesen't connect trying to connect even for dozen times and i had checked every paramaters multiple times and every thing is right?
And i knew later that should only have to do this ONCE per site and i knew my mistake now. How can i fix this now. Thanks.