Post Grid not showing Category Listings

Hi,

I am using Post Grid Pro, filterable grid.  The blogs are not shown when  I click the "category" listing.  For example, on this blog page,

https://origami-resource-center.com/dinosaurs-by-stanley/

if you click on one of the categories listed on the right sidebar, it pulls up an empty page like this:

https://origami-resource-center.com/category/animals/

When you move your mouse over the page, you see the pointer icon which suggest that the posts are present, but invisible.

Hope you can help, thanks!