After the categories get created in Prestashop, they need to be assigned to the products.
For this purpose:-
From Prestashop admin panel menu select Catalog > Products > Select the product to be edited and locate the Associations tab.
Now Select a category, among jet categories which has to be assigned to the product.
Select this Jet category as the default Category from the Default Category Dropdown List.
Click Save or Save and stay in order to save the updates.
NOTE:- A product can be assigned to a single category only as this is the specification of Jet.com and we have to follow it.
After assigning a jet category as default category you can see the default and Category Related additional Jet Attributes in the Jet Prestashop Integration tab.