I am unable to add my Halifax card to Samsung Pay via Curve app since Halifax is not directly supported with Samsung Pay. I get error when I click on verify card and it just says "Something has gone Wrong. Please try again later" I even tried to register on Curve app but it just says to complete the application process on Samsung Pay which again redirects to the same error. I am using S21 Ultra.
So Halifax is not supported by Samsung Pay and in order to add unsupported cards they are providing Samsung Pay PLUS which is through Patnership with Curve where you can add these unsupported cards. This functionality is however not working
I think I had my Halifax credit card registered on curve before, you just need to verify the code that's sent to the card. I connected my barclaycard too which also isn't supported by Samsung Pay. I had the issue that I already had a Curve card before I tried to connect with Samsung Pay, hence I never used it. Now you mentioned it and I recently checked, I can connect it to my Samsung Pay, so thanks for that.