Please try after some time or place a new order, If still facing the same issue please check the below points before applying any Offer/Discount.

1) More than two offers cannot be placed at a time on a single order.
2) Check the Offer/Discount code correctly before applying.
3) Check with the expiry date of the Offer.
4) Please check the terms and conditions of the Offer/Discount code before availing.