Were you successful in adding your credit/debit card to your Mac? Apple has the following set of steps in the support document
Add cards for Apple Pay - Apple Support
How to add a debit or credit card for Apple Pay on your Mac or iPad
- Open Wallet settings on your device.
- On your Mac model with Touch ID, go to System Preferences > Wallet & Apple Pay.
- On your iPad, go to Settings > Wallet & Apple Pay.
2.Tap Add Card.
3.Follow the steps on the screen to add a card.
4.Verify your information with your bank or card issuer. They might ask you to provide information.
On Mac models without built-in Touch ID, you can complete your purchase using Apple Pay on your compatible iPhone or Apple Watch: On your iPhone, go to Settings > Wallet & Apple Pay and turn on Allow Payments on Mac.