Can’t use iTunes credit
I got my son an iTunes voucher for his iPad which I redeemed and it says his balance is £15, but when he comes to purchase anything it takes you to a payments option in which my options are Apple ID ( balance £15.00) or credit/ debit card, I click on Apple ID but it just comes up to redeem or add funds? I don’t need to do either as there is already credit there? As it’s a child’s account he needs me to approve all purchases (even free games) but I’m not even getting a notification to approve 🤔
iPhone 8, iOS 13