Check the fine print for any exclusions or restrictions. Verify the expiration date to ensure the code is still valid. Ensure correct entry without typos, paying attention to uppercase and lowercase letters. Try a different browser or device to see if the code works there. Clear cookies and cache to refresh the browser. Disable browser extensions temporarily, as they might interfere with the code. Contact customer service for assistance if the issue persists. Search for a new working promo code if the current one is invalid.