Door dash promo codes disappearing?

So I’ve had this happen a few times where I see a promo that’s available and it says the end date is a week or so later. I’ll build my cart and plan to use the promo the next day when I do my delivery, but then the next day when I go to place the order, the promo completely disappears and the code no longer works for me… I always check the end dates of the promo codes so I know it’s not that. I’m kinda annoyed, does anyone know why this is happening to me?