I copied the plugin itself from the demo to the base game and that solves the problem. I used the version I downloaded after I bought it (a bit a go) but it said no new updates in 24 days or something, so I assumed I was good.
Anyway, great plugin. Is there a way I can resize the player inventory windows? I want an inventory like System Shock 2 (3 rows 10 columns, centered at top of screen).