Because the coupon was not valid at the time it was redeemed.
Typically, this means they tried to redeem the coupon after its end date (up to 28 days after its start date), which you specified during coupon code generation. In the Seller Office coupon page, coupons that can be redeemed have the status 'Usable', coupons in any other state cannot be redeemed.
Factors that make a coupon invalid (not redeemable):
- During the waiting period (about 24 hours after generation, coupon status 'Waiting').
- Another customer has redeemed the coupon code (coupon status 'Expired').
- The current date is past the coupon end date (coupon status 'Expired').
- You changed and updated the registration information of the coupon's paid app (coupon status 'Terminated').
- You terminated the distribution of the coupon's paid app (coupon status 'Terminated').
- Samsung suspended the distribution of the coupon's paid app (coupon status 'Terminated').
For details about generating and managing coupons, see Generate and Manage Paid App Coupons.