If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return. Click on Tax Tools on the left side of the program screen while working on the 2019 online tax return. Click on Clear & Start Over.
What does the error message say? If you registered or paid then you cannot clear. Federal record retention laws prevent that because after registering or payment you can print and paper file . Just abandon the account.