What could be stopping my ShareThis button from displaying?

My site: http://www.earthascope.com

For some reason, I can’t get the ShareThis button to display on my pages and I’m thinking there must be something in the theme preventing it.

It is supposed to display at the beginning of the post, directly after the Stumble link and in between the “:: ::”

Could someone please take a quick look?

Thanks so much in advance!