Category name disappeared from Category Page

As the title says, the Category name has stopped showing up at the top of each Category Page (which our site uses as a kind of menu). It was there until a couple of weeks ago, and I changed nothing in between. I tried deactivating plug-ins, but no luck.

When I switched from Cubic to the Twenty-Nineteen Theme, “Category:[name]” did show up. But when I returned to my Cubic-child Theme, the problem was back again. Yet Cubic hasn’t been changed in many months.

Can anyone explain what might have changed, and how I can fix it?

The page I need help with: [log in to see the link]