Blank "error" message when trying to create login

Hello! I'm trying to create a BCBS account using my insurance card so I can renew my plan, and although it accepts the identification number, and I'm selecting a username, password, and email in line with the provided guidelines, I'm getting a message that just reads "error" when I click Create Login.

The problem has persisted despite my trying several usernames/passwords/emails. Any idea why this might be?