Been having the same issue for about a month now! Such a pain. At one point they got it up and going, but just got my email this morning that my bill was due...went online to view and same error message.
Sorry you are having difficulty paying your bill online. An agent with access to your account will reach out to you directly by email, private message in the Forums and/or the billing telephone number on your Verizon account for more information or to help you resolve your issue.