I wondering that you are selling this feature which is obviously not working as you can still see on your demo page: http://themes.creiden.com/circleflip/builder-demo/circleflip-portfolio-cats/audio/
I first mentioned this problem on February 5 2016 with an older post, which is 8 weeks ago! I think empty category or tag pages are a serious problem, which should be solved immediately, especially if this bug is on your demo site. I’m disappointed.
It took me a while, but I fixed this on my own now. Categories and Tags are working very well now on my site as you may see on this tag-page:
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