Usually, that's because the discount doesn't apply to the things you've ordered. But also check the following:
- Is the discount code still valid?
- Is the discount code valid in the country where you order?
- Have you ordered products for the minimum amount?
- Some discount codes apply to specific products. Are they in the shopping cart?
- Haven't you used the code before? You can only use a discount code once.
If the answer to all the above questions is 'yes', then you are entitled to a discount. Please contact us so that we can check what has gone wrong.