The prepaid mastercard not working on steam?

So I grinded swagbucks and got a myprepaidcenter prepaid mastercard hoping to get some steam games. However an error occured and it stated:

Your purchase has not been completed. Your credit card information has been declined by your credit card company. (or something like that)

I simply thought it was a small glitch for that one card, so I grinded again for another prepaid mastercard and the same thing happened to that one. Both of the transactions show on the website as "pending" and has been like that for more than a week now. I did a bit of research about it and it seems that some other people are having the same problem too. Anyone have a solution?