I can display them in the app but then what?

I tried to use them yesterday on a flight. The flight attendant used my phone and kept trying to get the coupons to open. I can tap them all I want but they just sit there. If I tap my Platinum Medallion credential right below the drink coupons then that opens up into what looks like a code that can be scanned. After the flight attendant tried and failed to scan that code she went back to the coupons and tried to open them again to no avail. She said they are supposed to open but never having seen that myself I don't know what that looks like.

How are they supposed to work?