I bought two variables at $500 each and the discount did not come off. I showed the cashier the app with the coupon and she processed the discount manually.

I went back later that night (different shift) and did the same thing. Manager came over and said they had to be $100 visas (this store was out of those, but I wasn't interested in them anyway).

I do think it's worth asking/playing dumb as they may just give it to you.