I didnt have any sales tax. I got my order to go through and confirmation for both via email.
What I did was: click the "change payment method" button, enter your same credit card info, continue to check out with the greyed 1....worked for me.
OnSale: "Notwithstanding the order issues we have noted, right now if you validate your order ID that inventory unit will be set aside. That said, it is only "reserved" insofar as your payment ultimately goes through and you follow the terms and conditions and guidelines initially posted, including the limited time nature of the promotion. If you have a valid order ID we have every intention of helping you to get your unit. Thanks"