@SEA-user You have to sign onto your online account using the exact same User ID you used to create the online account to e-file the Form 4868.
To access your online account sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
If you forgot your User ID -
Close all TurboTax windows on your web browser (including this one). Copy and paste the account recovery website link onto a new web browser window and run the tool.
Use this TurboTax account recovery website to get a list of all the User ID's for an email address. Run the tool against any email addresses you may have used - https://myturbotax.intuit.com/account-recovery
If none of the user ID's received will access your 2019 account, then use the option shown in blue on the account recovery website, "Try something else"
