Rich snippet conflict?

Hi,
I’ve downloaded your rating plugin and it works fine on the site. The rating doesn’t show up in the Google rich snippet tool – here’s an example page: http://www.theansweriscake.com/gluten-free-angel-food-cake/ … in this case, the recipe microdata photo shows up, but not the rating.
Can you advise why it’s not working, and what can be done to rectify this?
Thanks

http://wordpress.org/extend/plugins/kk-star-ratings/