There may be several reasons why you are not able to use your discount coupon. You may be typing the code incorrectly, the code may have already expired, you may be trying to use the code on products with a promotional price and that is not possible because the discounts cannot be combined, you may be trying to use more than one code at simultaneous, etc. If you consider that none of these reasons are valid and the error persists, you can always contact us here.