Hey there ManMilk,
Thanks for reaching out to the Apple Support Communities. To get started, have you gone through the steps listed in the resource below to ensure that Apple Pay is set up correctly on your Apple Watch: Set up Apple Pay - Apple Support
How to add a debit or credit card to your Apple Watch
1. On your paired iPhone, open the Apple Watch app.
2. In the My Watch tab, tap Wallet & Apple Pay.
3. Tap Add Card.
- Tap Debit or Credit Card to add a new card.
- Tap Previous Card to add a card that you used previously.
4. Tap Continue.
5. Follow the steps on the screen to add your card.
6. If necessary, verify your information with the bank or card issuer. They might ask you to provide more information or to download an app before approving your card for use with Apple Pay.
If so, we'd also recommend ensuring that your Apple Watch and iPhone are both updated to the latest software versions as well. For help with checking for and performing updates on your devices, check out the additional resources below:
We hope that's able to help.
Take care!