Custom fields in Tab on product description page.

Hi,

That's how it is by default with the "tabular" layout of HikaShop.
So this means that your product page layout has been customized:
- either by your template provider, and thus you should contact them
- or by yourself, and you should know better than us what to do

A simple solution is to delete the customization of the product page layout view file (show_tabular) via the menu Display>Views and make sure that the tabular layout is selected in the "layout on product page" setting and you should get that tab. But that also means that you'll loose all the customization that had been done to that page.