There are two primary reasons why the "Add to Cart" button would not be showing on your category page:

  • Go to Settings→ Inventory Settings→ Products.
  • Enable Allow multiple products to be added to cart from the product list.
  • Go to Settings→ Inventory Settings Products
  • Enable Display add to cart on product list template and search results template.

  • If the "Add to Cart" button is displayed for some products but not others, it's likely that you're using variants (personalizations or options/option sets) on those products. 
    • If you have personalizations set up and they are required, the button will not be displayed on the product list page. You must go into the product detail page to choose a variant(s).