Site categories landing page include link and count but no linked sites

I've installed Site Categories with two categories; see here for landing page. I have manually set the category for several sites to test it, and indeed the landing page includes a link and count for each category, but clicking these links results in "It looks like nothing was found at this location. Maybe try a search?" I read this related post, but that's not my problem I'm pretty sure.

Thanks for your help --

Jim P.