There is a payment problem with a family member's previous purchase. Ask the family organiser to update their payment details.

The family organiser will need to update their payment method on their Apple ID. Instructions are found in the following link:

If you need to change or update your Apple ID payment method – Apple Support (AU)

This change is required as the payment method registered to the family organiser is the default payment method used for all family members when Apple Store Credit is not available to cover the balance of a purchase. This message occurs when a purchase is declined by the Family Organisers payment method for any reason.