Thanks for the link, though my issue was different … and I now understand why… When asked to enter card details, you are offered to enter them using NFC (tap your card on your phone) HOWEVER, when doing so, the details page asks for your postcode (and does not recognize a foreign, at least UK, postcode)BUT, when I enter the card details manually, you are not required to add a postcode! Therefore, I have now been able to add both my Amex and Mastercard via the app