Check the fine print for any exclusions or restrictions on the coupon code. Ensure the items in the cart meet the coupon's requirements. Verify the expiration date of the coupon. Try a different web browser or device. Disable browser extensions temporarily. Clear cookies, cache, and site data. Use incognito or private browsing mode. Contact customer service for assistance. Search for a new working promo code.
If these steps don't resolve the issue, it might be best to look for an alternative discount or promotion.