It may be caused by the following reasons:
1. You may enter a wrong Coupon code. Please make sure that you enter the coupon code exactly as you received it, with no space before, within, or after it. To avoid errors, we recommend you to copy/paste the promotional code you received.
2. The code has already expired.
3. The purchase amount is limited.
4. The discount is applied to the original price but not the sale price on the page. If the item is on sale or discounted more than the coupon discount, there might be not too much price difference after applying the coupon.
If you still have problems, you can contact customer service for help.