If it won't let you clear and start over and you haven't paid yet you can just leave this account and start a new account but you won't be able to transfer from 2018.
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...
