Apple Pay not working - payment not completed?

I am trying to renew my NYT subscription through Apple Pay. My Face ID/Passcode are seemingly accepted (no tick though) then I see 'Processing Payment' -> 'Processing' before a red exclamation mark and 'Payment Not Completed' appears.

I use Apple Pay regularly and successfully.

Could it have anything to do with the fact I am attempting an international transaction, UK to US? (£s are used though).

Any help would be great.

Many Thanks