In ProductCart version 3.1 and above the small "Add to Cart" button is sometimes shown on the category or search results page. Why is it not shown for all products?

The "Add to Cart" button is hidden when any of the following is true:

(1) Store is catalog only (no purchasing)
(2) Retail customers are not allowed to purchase (e.g. wholesale only)
(3) Stock Considerations:
- Item is out of stock and purchase of out of stock products is not allowed (global setting)
- Item is out of stock and back-ordering is not allowed
(4) Product is a Build To Order product
(5) Product is an Apparel product (so product options exist)
(6) Product has options and at least one is required
(7) Product has custom input fields and at least one is required
(8) Product has required accessories
(9) There is a minimum quantity, and it cannot be shown on the page
(10) The product is "Not for Sale"

Note that the small "Add to Cart" button shown is a different graphic from the regular "Add to Cart" button shown on the product details page. This button was not used in previous versions of ProductCart, so review it/edit it using the "Settings > Edit Store Buttons" area of the Control Panel

To completely turn off this "Quick Buy" feature (hide the "Add to Cart" button), please see this other FAQ.