"Apple account not enabled for online (or in app) purchases"

I recently got a $150 gift card that has been redeemed to my Apple Account, which has been added to my Wallet. According to the card in my Wallet it's "Ready to Use. Pay with your iPhone in the Apple Store, shop online, or buy apps, subscriptions, and other services". However, when I try to use the Apple Account/Gift card for a purchases, it says "not enabled for online purchases", and I can't select Apple Account to pay. I read online that Apple with automatically use Apple Account funds FIRST, then take remainder from back up card, however what I purchased an iPad, the entire charge with to my Apple Card, not the gift card account. How to I enable my Apple Account for online or in-app use?