payment cards are not accepted for this account

My daughter is 13. When I go to add her card to her Apple Pay, before it even asks for the bank card it says “payment cards are not accepted for this account” but I don’t even get a chance to say the account details. So it must be an issue with Apple. I thought you could have Apple Pay from 13. She has the latest software and no outages etc. So I don’t understand where the problem lies. I’ve tried googling it but it always takes me to the same support page which doesn’t help with my query.