No longer can use a previous category to a subcategory and cannot assign (same) category
I've been using a specific Category and Subcategory for years. However within the last month I'm no longer able to use that category:subcategory combination. It shows up in my Category List under Tools but when I try to use it, it asks me if I want to create a new category with the subcategory name. I'll say yes and everything fills out properly in the next screen but when I hit save it says "You cannot assign this category to this category group." Has anyone run into this and what can I do to fix it? This has happened to a number of category/subcategories I've been using so it's not specific to just one category.