Hi,
Please check the following in the HikaShop backend:
- -> System -> Configuration -> tab Features -> Main: option "Catalogue mode" must be set to "No". (Otherwise no Add To Cart buttons.)
- -> System -> Configuration -> tab Display -> Default parameters for products: option "Display 'Add to cart' button" should be set to "Yes".
- -> Display -> Content menus/modules: in all product listings, under "Parameters for products", the option "Display 'Add to cart' button" can be set to "Inherit" if the default was previously set to "Yes", or must be set to "Yes".
Don't forget to save if you changed option settings. Make sure you have no cache enabled on your site, then reload the frontend and see if the buttons appear.