Greetings, hoolie.
When adding a card to your Wallet, you should use the following steps:
"Add a credit or debit card
- In Wallet, tap
. You may be asked to sign in with your Apple ID. - Choose one of the following:
- Previous cards: Choose the card associated with your Apple ID, cards you use with Apple Pay on your other devices, or cards that you removed. Tap Continue, then enter the CVV number of each card.
- Debit or credit card: Position iPhone so that your card appears in the frame, or enter the card details manually.
Alternatively, you may be able to add your card from the app of the bank or card issuer.
The card issuer determines whether your card is eligible for Apple Pay, and may ask you for additional information to complete the verification process." Set up Apple Pay in Wallet on iPhone
If you are following those steps and still unable to add your card, Restart your iPhone. Restarting can often help resolve unexpected behaviors. Also, ensure that your iOS is up-to-date: Update your iPhone, iPad, or iPod touch
We hope this helps!
Sincerely.