Several explanations are possible :
1. the discount code is expired.
2. The code is valid from a certain purchase amount or on a specific product.
3. Your order already has a code or an offer ex: -50% on the 2nd product (the codes cannot be combined, you can only use 1 code per order)
4. You are trying to activate a discount on a gift card (discounts are not active with gift cards)
For more information, please contact our customer service by sending us a message.