Similar Posts Not Showing (Says None Found)

This plugin used to work for me like a charm. I am not sure when I deactivated it earlier, but today when I reactivated it, and set it up, it just continued to say “None found” under Similar posts on the site.

– I am using latest WP version.
– I have the post plugin library plugin activated.
– I am using Thesis theme 1.8.
– I was previously using this code: <?php if (function_exists(similar_posts)) { similar_posts(); } ?> to show it below the posts and it used to work. I tried replacing it with <?php similar_posts(); ?> to see if it works now, but it doesn’t.

I have played with the options on the plugin settings but it just won’t show the similar links for some reason. Please help.

http://wordpress.org/extend/plugins/similar-posts/