Why do you want to start over? 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-onli...
