"Card Not added" error - Apple Pay

I received a new debit card yesterday, since my old one had expired. I deleted the old one from Apple Pay in the Watch app, and now when I try to add the new one, I am presented with the terms and conditions, and then a "Card not added - Contact issuer" error.

This happened with my old card, which I solved by signing out of Family Sharing. I am still not part of a Family Sharing group. At the time, HSBC said it was not on their end, and was an issue with Apple/device.

With my new card, I can add it to my Dad's Watch, so it is definitely not the card or bank account. Region on my phone and watch is UK.

So far, I have hard reset, turned off and back on, signed out and in again of iCloud.

Apple Watch Sport (watchOS 2.1) iPhone 5s (iOS 9.2.1)