[Plugin: Simple Social Buttons] facebook button dosn't work

hi,
I’m using the plugin on the website diegoruvidotti.com, for example in this category:
http://www.diegoruvidotti.com/category/blog/
twitter and google plus work perfectly. facebook’s like button dosen’t work. It seems to work but no comment appear on facebook…
can someone help me?
thanks a lot

http://wordpress.org/extend/plugins/simple-social-buttons/