Payoneer card rejected by website to make a purchase

Hi, I just tried buying something on a website here in Argentina called "Mercado Libre," which is similar to "eBay." I bought something already last week, so I know it worked before. I have more than sufficient funds on my card, and nothing has changed from last week when I bought something else.
Now, it says I should contact my card provider to Authorize the purchase... Why should I do that, and how?
Thanks!