10yr old can’t use their Apple balance for purchases.

Help me please!

I’m a parent with a 10yr and 12yr old.

I have removed my credit card as a payment method after too many times apps avoiding the ask a parent check and charging my credit card without permission.

HOW DO I GET THE APP STORE TO USE MY CHILDS APPLE BALANCE AS A PAYMENT METHOD.

She using her IPad.

She has a Apple balance of $68 but is unable to buy a $3 in app purchase using her

Apple Balance.

Apple states that Apple Account Balance is a valid payment method and yet it won’t take the available funds for a purchase.

Greatly appreciate any help.