Double-check the coupon's expiration date and scope of application to ensure it complies with the usage rules. Verify the coupon code with the website's customer service to see if it is still valid. The website may have changed or canceled some promotions. Ensure the coupon code is entered correctly without any typos. Clear the browser cache and cookies, then try applying the coupon code again. Use a different browser or device to see if the issue persists. If the problem continues, contact customer service for further assistance.
