So you did not notice that you did not actually pay your tax due for those years or that you did not receive a tax refund?
Now you will need to print, sign and mail in those tax returns. They cannot be e-filed. If you owed tax due, you are late, so you can expect a bill from the IRS for the penalty/interest, which will be calculated by the IRS based on when they receive your payment and how much you owed. TurboTax will not calculate that. If you are getting a tax refund, there is no penalty for filing late.
Online preparation and e-filing for 2016 and 2017 is permanently closed. You have to download the software to a full PC or Mac (not to a mobile device) and then print, sign and mail your return. If you already paid for your TurboTax software, you can contact customer support to push a download of the software to you.
To call TurboTax customer support
They are available from 5 a.m. to 5 p.m. Pacific time.
To finish a prior year return started in TT online:https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS and/or your state received the return.
All you can to now is print and mail the returns as requested ... when you do download the PDF look for the filing history page to see if the returns were accepted or rejected.
To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)