After you file

2017?   Now it is 2024.    TurboTax never gets any information about your tax return after you file it ---TT cannot find out about this for you.   You say you mailed it before the filing deadline--which would have been in April 2018----six years ago.   If you used a mailing service with tracking--like certified mail--then you have some proof that you mailed it timely.

You have to deal with the IRS---TurboTax cannot assist with this.   You can call them to see what happened, or see if a Tax Advocate will help you.   

To  call the IRS:IRS:  800-829-1040  hours 7 AM - 7 PM local time Mon-Fri

Listen to each menu before making the selection.

First choose your language. Press 1 for English.

Then do NOT choose the first choice re: "Refund", or it will send you to an automated phone line.

Instead, press 2 for "personal income tax".

Then press 1 for "form, tax history, or payment".  

Then press 3 "for all other questions."

Then press 2 "for all other questions."  It should then transfer you to an agent.

TAX ADVOCATE

At the following IRS website, find the USA map and click on your state, and it will give you the number of your area's IRS Taxpayer Advocate.

http://www.irs.gov/uac/Contact-a-Local-Taxpayer-Advocate

Also see this article for more info on how the Taxpayer Advocate Service works::
http://www.irs.gov/taxtopics/tc104.html

https://www.taxpayeradvocate.irs.gov/wp-content/uploads/2020/08/TAS_CaseCriteria_061120.pdf 

https://www.taxpayeradvocate.irs.gov/can-tas-help-me-with-my-tax-issue/