"Update Your Family's Payment Method" Error message in Sibley Birds 2 app in Family Sharing

Family sharing active. Family member can see my apps. App is available to share (Sibley Birds 2). Attempting download results in error message, “…update your Family’s payment method.” (A) Method (PayPal) IS up to date and (B) changing to a different valid method (credit card) did not help.

[Re-Titled by Moderator]