The principle is stating that if anyone creates an unfair situation (in this case, the corporation labeling the coupon with an incorrect expiry date), then they must rectify the situation.
But in E, we do not know if the reason for denying the customer the coupon was the company's fault or not. Therefore, we cannot make a judgment saying that they should or shouldn't rectify the situation.
Look at C, it says the issue that the customers may have is due to the expiry date, which we know the company is at fault for. That's why the corporation should fix that issue.