Double-check the coupon's expiration date and scope of application to ensure it complies with the usage rules. Verify with the website's customer service to see if the coupon code is still valid. The website may have changed or canceled some promotions. Confirm the coupon's source to ensure it is not from an unrelated website. Check the website's compatibility with the coupon function, as some websites may have integration issues. If the problem persists, consider reporting the issue to the website's support team.
