Tried to Clear and Start Over but Turbo Tax says I cannot because I've registered. What is registered?

Have you already submitted and filed your taxes? If so, you will not be able to clear and start over. More assistance with this has been provided by clicking here.

Or if it doesn't let you clear and you haven't paid or filed you could just start a new account.  Online is only good for 1 return per account.  But you can use the same email address for 5 accounts.   How to start another return in the Online version

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596