Unfortunately, with it being the weekend, it's possible that the problem won't be fixed until Monday.
I was going to do a quick check then post the steps to try to help you get your order completed, but I'm seeing problems as well, for which I started a new topic. Actually, not just the Voice ordering page, but quite a bit of the MyAccount site, and what makes it harder to discern is that it appears to be an intermittent problem, as sometimes it worked.
Still, it's possible that whatever is causing it will be fixed soon. I'm keeping my fingers crossed.