Error message

Hello, I followed the detailed plugin install instructions at http://takanudo.com/jsl3-facebook-wall-feed/

I´ve created the app, then I´ve entered the “Facebook ID” and the “App Secret” in the plugin settings.

When I save changes I get this message:

Error
An error occurred. Please try again later.

do you have any suggestion?
Please tell me if you need more detailed info about my procedure

Thanks!

http://wordpress.org/extend/plugins/jsl3-facebook-wall-feed/