wp-pagenavi missing on category pages

I’m using a theme which has the plugin built-in (http://templatic.com/demos/ecommerce/?page=store)

As you can see, the navi shows up on the link above. However, on the demo site, as well as on my own, the navigation does not show up on any CATEGORY pages.

In the Reading setting for WP, I have set display to 6 posts (6 products in this case). When I click on a category with more than six posts, only 6 show, and no navigation pages are shown. Looking at the source with firebug, I see there is no pagination div inserted when viewing a category page:

<div class="pagination">

                 <div class="Navi"><strong class="on">1</strong> <a href="http://shop.dearearth.net/?s=neck&x=0&y=0&paged=2">2</a> <a href="http://shop.dearearth.net/?s=neck&x=0&y=0&paged=2"><strong>»</strong></a></div>
            </div>

Any clue how I can add so that the navi code is included in category pages?

Thanks!

P.S. I have sought help from the template provider, but they redirected me here.