After you file

Are you using the Mobile App?   If so, it will be easier to troubleshoot if instead of the App, you log into Online TurboTax using a browser, preferably on a computer, but you could use a browser on your mobile device if it's secure.

Or did you already log into Online TurboTax with a browser and only saw 2016, 2017, and 2018?

 You may not be seeing the earlier returns if they are in another account.  If you don't find them in that account in Online TurboTax, we can tell you how to look for multiple accounts (User IDs).