At the outset, I want to apologize for the email notifications you've been getting about "billing attempt failures", or "rebill attempts exceeded". This affects all MasterCard payments. This is not the experience I want to provide, and this ordeal has been hugely embarrassing for me.
I've been using payment services from 2checkout, who seem to have run into an issue with MasterCard payments. They have not been very transparent about the issue, and kept dragging their feet about the problem despite repeated requests to fix it soon. Today they sent an email saying that the issue won't be resolved for another month!
What you can do
If you are one of those who's affected, 2checkout would have already sent you a mail with a link to update your payment information. Please use the link to pick a different payment method (they still support Visa, Amex and Paypal among others). If you only have a MasterCard card, you could update your payment method to use Paypal and make a MasterCard payment through them. You don't need a Paypal account for this.
If you have already updated your payment information, huge thanks to you! You rock!
If you are paying for a new account, you won't have the MasterCard option when you checkout, but you will be able to use any other card, or use Paypal to route your MasterCard transaction.
If either of these is not possible, please get in touch with me at rakeshpai at errorception dot com, and we'll take it from there.
I know that this is annoying for you, and it's annoying for me to have to put you through this. This has been an embarrassing ordeal for me over the last few weeks, and I will continue to chase 2checkout until they resolve this issue. I wholeheartedly apologize again.