Why does TurboTax 2021 say I haven't e-filed, after I did and IRS has accepted it?

You might be logging into another account.  For more details on how to check how many accounts you have, please see the Help Article here.  

I only have one account.  And I didn't log out and log back in during the time between when I e-filed the form and got the TurboTax email that the IRS had accepted the filed form.