This is one of the problems customers encounter related to the function: Product Multi-Tab.

The problem you do not see tabs on the Product page occurs when you enable Multi-Tab in Customize Theme> General settings> Product Page > Product Multi- TabsĀ 

While the introduction of your product does not have the H5 tag in the content so our theme can not display the tab content. To fix this problem you can disable this function and the website will display tab by default.

When you turn on the Multi-Tab function, you need to add Heading 5 content tags to the Description text for the product.