Pay with a like - Facebook button won't show up

Hi there,

I've successfully implemented your great plugin "Pay With A Like" on my site and was able to display three buttons - linkedin, twitter, and facebook. Everything worked fine.

A few days ago I recognized that the Facebook button won't show up anymore. I've double-checked my setting but couldn't find anything wrong or unusual. I've also re-created the Facebook App to be used.

Can you guys please help?