sub categories not showing up when click sub categores

Hello everyone. I know a lot of people posted this topic. However, I searched all related topics. My problem can still not be solved. I do need your help.

My website is https://www.remyqueenonlinestore.com There are sub categories of "Straight style", "Wavy style" and "Curly style" under category of "Stock Full Lace Wigs". When you click "Stock Full Lace Wigs", you will go to a page and you will see the sub categories, pls check the below link and pic:
http://www.remyqueenonlinestore.com/stock-full-lace-wigs-1/

However, the problem is that in this page http://www.remyqueenonlinestore.com/stock-full-lace-wigs-1/ After you click the sub category in the left, the sub category will disapprear, pls check the below link and pic.
http://www.remyqueenonlinestore.com/stock-full-lace-wigs-1/straight-style-7/

Thanks for your reply.

is there anyone who can help me?

A fresh clean uncustomized install of Zen Cart works properly.
Therefore your problem is in one or more of your addons/customizations.
Simple way to find out potentially problematic files: http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Diagnosing_Obscure_Issues

can you give me any clue? there are huge documents there. SHould I check one by one?> DrByte:

A fresh clean uncustomized install of Zen Cart works properly.
Therefore your problem is in one or more of your addons/customizations.
Simple way to find out potentially problematic files: http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Diagnosing_Obscure_Issues

I can tell you what I already told you: a clean install doesn't exhibit those problems.
And if you follow the instructions in the article I gave you, there are some automated comparison tools there which can help you quickly which files aren't the same as in original Zen Cart files.

You obviously have numerous custom alterations in your site. It's impossible for me to guess which ones are specifically causing your problems. I have given you the tools and guidance you need in order to do the research yourself.