Not sure if this is BB specific but after some help.
Doing a WooCommerce site for a client and currently building the category page (http://penguinpreview.co.uk/kulushoes/heels/)
The widget for the product categories is fine and as you can see, displays fine. The widgets for recently viewed products displays nothing, not even the title. Also the widget for WooCommerce Layered Nav doesn’t display the attribute “size” even though it’s set. I just wanted a sidebar option where visitors can select their shoe size and would show all products in that category in that size.
I just tried the Recently Viewed Products widget and it works fine on my end. Is your site live? A product should be viewed by a non-logged in user before it gets reflected. Try visiting a product logged out or via incognito/private window.