prepaid topup with a foreign credit card not accepted

Hi, I travel to the US occasionally and have a prepaid Sim with gold rewards status which I topup yearly to keep the account active.

I just tried to topup again and have tried using several non-US issued credit cards (visa and master) but it shows a “card number is invalid Pls try again” message after I enter my credit card number.

Any idea what's wrong?

Gracias