Quick answer: Check the offer type first. If the date is recent, the usual causes are an excluded product, a first-order-only code, another discount blocking it, or a typo.
1. The code has expired
Vendors end promotions without notice. Look at the status next to the code. A code still circulating online may have stopped working.
2. It is for new customers only
First-order codes are rejected on an account that has already ordered. Terms such as "welcome discount" or "new customer offer" usually mean this.
3. The product is excluded
"Eligible products" means selected items only. Sale items, bundles and kits are common exclusions. A sitewide code can still skip some categories.
4. Another discount is active
Some stores allow one offer per order. A sale price or a member discount can block a code. Try removing the other discount to see whether the code applies.
5. The vendor changed the code
Codes get renamed and retired. If a code stops working, look for a newer one for the same vendor on the coupon table.
6. The promotion ended
Seasonal and limited-time offers close on a set date. If the offer was tied to an event, it may simply be over.
7. The code was typed wrongly
Use the Copy button and paste the code. Remove any space at the start or end, and check for letters that look alike, such as O and 0.
A quick test before you pay
Add the item to your cart, enter the code and read the new total. If the total did not change, the code has not applied, whatever message appears.
FAQ
Does a working code always lower the total?
It should, but only for eligible items. Always read the final total before paying.
Where can I find a newer code?
Check the coupon table for the vendor, sorted by discount, and compare the percentage and what it applies to.