Not working

I haven’t seen the categories duplicated before. Can you confirm you don’t have categories with the same labels, but with different IDs?

As for it not working, it’s hard to know. Sometimes themes do things in an unexpected way causing the behavior of my plugin to be different than what’s expected. There are no “tricks” or hidden settings with the plugin so if it doesn’t do what you expect, I wouldn’t spend too much time trying to get it to work.