[Plugin: SEO Slugs] SEO slugs does not work upon activation

I downloaded and installed this seo plugin just as it instructed and while I’m editing a post, it does not change the link like it says it should. The normal permalink structure with special characters and unnecessary words stays there (like is, as, the, and similar ones).

I’m thinking it’s because of my custom permalink structure which currently looks like this:

/%category%/%postname%-%post_id%.html

But I’m not completely sure. If anyone else out there can give me any ideas, I’ll try them. I’m just afraid to change my link structure since i have thousands of links using this structure already.

Any help, definitely appreciated.

Help!!