Sonja Great. Then you should meet all requirements to use your card with Apple Pay. The good news is: it should work just fine for you. As for why the button doesn't show up as expected, I'm not sure. As Thijs already mentioned, contacting the bunq Support might be a good idea!
However, you could also try to add the card manually to the Wallet app on your iPhone and see if that works. The steps are explained in the article linked to by Thijs, and I'll also put them here for convenience:
- Open the Wallet app.
- Tap the "+" sign in the upper-right corner.
- Do not tap on bunq, but instead scroll to the bottom and select “Add a different card."
- Click the bottom blue text to enter card details manually.
- Enter you name, card number and CVC as instructed (you should be able to get this information from the bunq app).
Not sure if this'll work out better for you, but it's worth a try I think :)