Weird situation that I looked at earlier in Sub Categories DON"T display in side menu.

When most top cats with subcats (e.g.Birkenstock) are clicked from sidebox or header dropdown menu, a subcat product listing displays instead of the subcat listing, and the sidebox doesn't expand to show the subcats or highlight the current cats.
When the dropdown is followed to a subcat and clicked, the correct subcat product listing displays and the sidebox shows top & subs, with current path highlighted.

One or two categories with subcats (e.g. Sendra Boots) work as normal.