I am having the same issue. I tried to login and it asked me for additional verification, meaning an account number to credit card, mortgage, etc. I attempted with my auto account number as well as two different credit cards (not debit). All accounts are well established - not new - however, the site would not accept and now I am locked out with the same registration error. The site says to attempt in 24 hours - I waited 3 days so far but still cannot access. There is no technical help at the IRS apparently. This is terribly frustrating - they ask for something that they do not accept, then lock me out of my account 😕
