I have had an issue like this in the past. Yeah, it is easy to use a code, but there is a pretty easy way to mess it up too. The code isn't a discount, it turns on the ability to choose a discount. And that is a bit confusing. It seems like there used to be a pay window that also allowed the code. But I can't remember exactly now. I do remember messing up the first time they did this by entering the code at the wrong place. THEN the next time they offered one, I was very deliberate in my selections, and messed it up again, because I was still treating it like a discount coupon. Now I know, enter the code, then check your discount. But it isn't intuitive. It is something you have to learn is different. Once you learn it, yeah, it seems simple enough. But it is easy to mess up too.