I just did it successfully, after getting the error you got the first time through. You're right, the website does not clearly have a place to log in -- you have to request a document or initiate a payment in order to get the login screen, wherein you can also create an account. In defense of OP, this may be the reason they did not include a link to a login page -- there doesn't appear to be one.
But to your point, there seems to be a bug in the form, where if you put any punctuation or special characters in the required passphrase, it misreports the issue as a bad password. Taking the exclamation point out of the passphrase caused my password (a different token) to be accepted. For what it's worth, YMMV, etc etc. (This is the government we're talking about...)