IN-Post Ads Not consistently showing up

Hi,

I am trying to use In-Post Ads so that a blog post about "weight-loss" will pull ads on that topic and inject them at the beginning, middle, and end of the associated blog post.

However, when I try using the plugin, here is my result: http://screencast.com/t/SI0nN3cpU0g

Does anyone know why I would be getting inconsistent results like this?

Thanks