I just installed and activated the plugin. I deactivated Akismet. I can see that Invisible Defender is installed because the line "Protected by Invisible Defender. Showed 403 to 0 bad guys." is showing up at the bottom of my comment form. But bad spambot comments are getting through. So far 4 obviously bad ones have come through and held in moderation instead of blocked. It has not blocked anything.
I do have
<?php wp_head(); //we need this for plugins ?> in my header.
Any ideas why it's just not working at all? My site is http://fakeplasticfish.com.