Having issues using Apple Pay in game app

I continually have problems (declines) trying to use my credit card (I’ve tried 3 different cards) on a Game app. I’ve tried everything I know to do. I’ve completely removed the card and then re-entered it, I’ve turned my iPhone off and on, I’ve changed to a different card (3 times) and it continues to decline my purchase.

It’s not my cards (2 I tried have “0” balances. I’m concerned I’ll try to use it to purchase something like groceries and it won’t work...that would be embarrassing!!

It’s getting VERY frustrating. Can someone with Apple Support please help me with this?