My 10 year old son has a hand me down iPhone XR, when I try to add a credit card in the Wallet App, it tells me Payment cards are not accepted for this account. How do I fix this?

We are headed to Paris in a week and a half and I am trying to purchase 10 t+ tickets for him to use Paris Metro using the IDF Mobilities app to purchase them, but the transaction is stopped because the tickets are not able to be loaded into his Wallet App. I am using his iPhone XR, IOS 17.6.1, how do I fix this problem. Thank you.