How do I add iPhone cards to Wallet on MacBook when 'next' button is greyed out?

I have wallet successfully set up on my iPhone. Today I'm trying to pay for something on my MacBook and Apple Pay claims not to have any cards on it (although I think I've it before).

When I go to 'add a card' it lists ALL the cards on my iPhone with blue ticks next to them.

If I click 'continue' I get a pop-up with a picture and basic details of one of the cards and three buttons "add this card later" ,"back" and "next" - which is greyed out.

Add it later means it doesn't get added

back means it doesn't get added

and next, presumably the one I want is greyed out.

If I select "add this card later" it just cycles onto the next card in the list - same again until I've agreed to add them all later and achieved nothing.

Seriously, I do not want to waste another hour filling in the same form again on the phone just spoke I can actually pay the bill at the bottom.

[Re-Titled by Moderator]