I have been using the same US mastercard on MercadoLibre for years. I used it as recently as Friday. But yesterday when I went to buy something, the card wasn't listed on my payment options. So I tried to enter it again at checkout and I got a message that "The operation doesn't accept this method of payment" ML chat told me to delete the card and re-enter it. I deleted and tried to re-enter it. No dice. I tried two other US a Visa and an Amex and it wouldn't accept them either. I got the reject message before putting in the entire number, so I don't think it is specific to my card. Any ideas?