Not getting pingbacks

I’ve seen many posts here about not receiving pingbacks, but I haven’t found the answer for my site. I have them enabled in both the Discussion settings and the Thesis theme page settings, but not receiving them (i.e. from this post: http://www.seodblog.com/michigan-seo-web-marketing-tutorial/)

My site is http://www.michiganseo.us

Thanks,
Jeff