Check the fine print for any exclusions or restrictions on the coupon code. Try a different web browser or device to see if the code works there. Disable browser extensions temporarily, as they can interfere with promo codes. Clear cookies, cache, and site data in the browser settings. Use incognito or private browsing mode to avoid issues with stored data. Contact customer service for assistance if the code still doesn't work. Search for a new working promo code if the current one is invalid.