ecart not adding a product with different size

Hi,
When I click to add a product to the cart and choose a tab size it adds, then I go back and choose a different tab size of the same product and it just adds one more to the product already in the cart. I am using a formula that I have used before, that works. Now it is not working on this particular site. Could you take a look at the detail.php and the cart.php.
Thank you.

To make it so that you add a unique item for each different tab size you should first go into your cart object and click on the columns tab. In here find your tab size column and check the box for unique. This will make it so that any item with a different tab size should be a unique item in the cart.

In the add to cart server behavior you can also specify how to react if the item is already in the cart, you can choose to sum, ignore, add new, or replace the item.