Discount not Applied to Web Order after Advanced Promo Code is Accepted

When using Advanced Promo Codes, there are instances wherein a promo code is accepted but no discount is applied to the webstore order. For these types of instances:

1. Navigate to Lists > Marketing > Promotions.
2. Click the Edit link of the promo code in question.
3. Check the Discount tab and make sure that a discount has been set up there.

*Note: Selecting a Discount Item in the main screen of the advanced promo code does not apply the discount to the order. It has to be set up in the Discount tab of the Advanced Promo code.