You cannot print your tax return or the extension until the TurboTax account fees are paid. Your message shows that you are using the TurboTax Live Basic edition which includes Live CPA support. It is NOT the Free edition.
Clear your tax return and start over with the Free edition. Complete the tax return using the Free Edition and register the Free Edition. Then you can print your tax return to include the Form 4868 Extension request.
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 and start over with a lower priced edition. Click on Tax Tools on the left side of the program screen while working on the 2018 online tax return. Click on Clear & Start Over.
