John Levine wrote:

FWIW, my US issued cards work fine as Oyster cards.

I can use my US issued Visa card to top up my Oyster card at an Oyster terminal
in the station, and I can enter it as a payment card on my Oyster account web
page, but when I attempt to actually top up my Oyster card, the transaction
fails. It also failed last week when I attempted to use the same card through
Android Pay on my phone.

Interestingly enough, when I tried my Amex card, I actually got an alert from
AMex stating that they had processed the transaction, but it never actually
completed on the Oyster end and failed the same way.