I have just added this plugin and find that so far no similar posts are found. Maybe it needs a new post.
Later
There is a lot of configuring to do with this plugin. First you need to go to settings and change settings in Similar posts as well as Similar posts feed. You also need to recreate your index by going to the plugin and seeing the link to this and then click on ‘recreate index’
Now it is working. Oh and you have to add some code to your index page.
Later
Wrong. It is only picking up the post that is written, not past posts. I’ll have to read more about this one. Or maybe it doesn’t picks up posts retrospectively even though I have installed a past post plugin.
Any ideas out there?
I contacted the maker of the plugin and he said “I notice you are restricting the output to posts which match both the categories and tags of the current post.”
Changed that, so now it is working