I put a link at the bottom of the quote page to up-sell a service plan on tires within the cart.
<a href="/checkout/cart/add?product=<?php echo $id?>&qty=4">Add</a>
The problem is that the cart doesn't display the added product when the cart page refreshes.
I debugged the CartController and the product is added and saved correctly. But when I debug the cart template the newly added item is not displayed.