Hi dsflkghjsfdlkyjsrtysrth,
Welcome to the Apple Community.
Re: I have an Apple Card. I cannot add the card to Apple Wallet on Mac.
Let's see if following Apple Support's online guidance works for you.
Seems you may need to be signed into your Mac with the same Apple ID that you used to apply for Apple Card.
Sign in with your Apple ID - Apple Support
says:
Sign in on your Mac
Choose Apple menu > System Preferences.
Click Sign In.
Enter your Apple ID and password.
If prompted, enter the six-digit verification code sent to your trusted device or phone number and complete sign in.
Apple support's article: How to add Apple Card to your Apple devices - Apple Support
says:
"To add Apple Card to Wallet, you need a Mac model with Touch ID.
If you have a Mac model without built-in Touch ID, you can turn on Allow Payments on Mac to complete your purchases on your eligible iPhone or Apple Watch:
On your iPhone, open the Settings app, tap Wallet & Apple Pay, then turn on Allow Payments on Mac.
To Add Apple Card to your Mac
Update to the latest version of macOS.
Go to System Preferences, then select Wallet & Apple Pay.
Click the plus button (+).
Select Apple Card, then choose Next and follow the steps on your screen.
You can make Apple Card your default card on your Mac.
This makes Apple Card your default card when you use Apple pay on your Mac".
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Re: Cannot add any card to Apple Wallet on Mac:
Use Wallet & Apple Pay on Mac – Apple Support
says:
" If your Mac or Magic Keyboard has Touch ID, you can use it to make payments on websites that support Apple Pay."
To add a card to Wallet: See the steps to follow under "Set up Apple Pay on your Mac" in the above article.
Hope this helps.
All the best :-)