I think there's nothing in the block because you haven't put your one product into a category yet - the Catalog block only shows subcategories when they have something in them. Go to admin/store and you should see a status message that tells you if you have unlisted products - follow the link to move the product into a category. You might first have to go to admin/content/taxonomy to add subcategories to your Catalog if you haven't done so already.