Did you canceled another registration attempt or not confirm the e-mail ?
Then the username of the former registration attempt may still be blocked.
Or another user has meanwhile used the desired name.
Wrong e-mail address ?
You can not activate your account without confirming it by clicking a link in our subsequent confirmation e-mail.
So your e-mail address must be correct.
Forgot to fill out all form fields and clicked 'Confirm' ?
Then you need to reenter your desired password since for safety reasons this is not stored within your online session!
Under 18 ?
Minors under an age of 18 years can not sign up for a cocompose "Creative Account".