Family member can't verify payment methods

You are receiving this error due to "purchase sharing" being turned on. Apple's policy is that when purchase sharing is turned on, the family organiser has to be the one who pays for everything. They want a single purchaser for sharing purchases.

If you turn purchase sharing off, each family member can then add their own payment method and pay for their own subscriptions.

Blame Apple for this absurdity but this will solve your problem.

Hello!

I was experiencing this same issue today and it is truly frustrating. My partner is the family organizer so I was the one being hindered. Long story short what I found was if I logged in to my Apple account on the web, went into payment methods that way I was able to add the security code and update the payment method. This then allowed me to make the purchase I was trying to do. Hope this works for you as well!