User error?

I have no idea what all the "Id give it zero stars if I could" reviews are about. Ive used the app for at least six months. Probably once a week. Ive had this work properly for me every time Ive attempted to use it, except for once. And that time, the person on the register gave me the item free because we couldnt get the coupon to apply right. Open app. Scroll down. Select deal. Scan barcode. Save money. Too complicated for the McDonalds haters, I guess.

Upp! about McDonald's, v5.5.1