TurboTax online and e-file for 2019 ended on Oct 15, 2020. 2019 (and earlier tax years) can now only be completed using the CD/download software installed on a Mac or Windows computer. The return must be printed, signed and mailed.

2017-2019 software can be purchased here:
https://turbotax.intuit.com/personal-taxes/past-years-products/

See this TurboTax help article:

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...

"How do I finish a prior-year return that I started in TurboTax Online?

If you started your 2017, 2018 or 2019 return in TurboTax Online but weren't able to file it before the shutdown, you can finish and paper-file it in the TurboTax download software for PC or Mac.

Start by purchasing and downloading the software and install it on your computer. If you're also filing a state, be sure to download and install the corresponding state program (PC instructions | Mac instructions).

1. Now sign in at TurboTax.com using the same login you used to prepare your prior-year return.
If you don't remember it, try account recovery. Still no luck? Then just start over in the TurboTax software you downloaded and skip the rest of these instructions.

2. Under Your tax returns & documents, select Download .tax file (not the PDF) for the prior year you want and save it to your computer.

3. Back in the CD/download software, select Find a Tax File, and then browse to the tax data file you downloaded in the previous step.

4. Select the file and click Open.

5 . You can now finish up in the software. Your return will need to be paper-filed, as e-filing prior years is no longer available."

A 2019 return cannot be prepared in Online TurboTax.    The website is currently only for 2020 returns.   Do NOT try to prepare and file a 2019 return using the Online website.

If you want to use TurboTax to prepare a 2019 return, you'll need to use 2019 desktop software (CD/download).   You can purchase 2019 desktop software directly from TurboTax as a download at this page and install it on your computer:
https://turbotax.intuit.com/personal-taxes/past-years-products/

Did you already pay for a 2019 online product?  If so, TurboTax Support should furnish you the software.  If you want to work on the 2019 data file you already started online, you can download the *.tax2019 data file, or you can start a new 2019 return from scratch when you have the 2019 desktop software.

You may be able to still find the 2019 software cheaper at a reputable authorized retailer like Amazon, but even there be sure it is a legitimate authorized product from Intuit sold directly by Amazon itself, since there's no way to be sure all third-party sellers on Amazon are legitimate.   Here's a list of authorized retailers:

https://ttlc.intuit.com/community/choosing-a-product/help/where-can-i-buy-the-turbotax-software/01/2...

Be aware there are "too-good-to-be true" Internet scam sites selling fake or pirated software.  Only companies in the above FAQ are authorized for legit TurboTax downloads.

Minimum system requirements for Windows version:
https://ttlc.intuit.com/questions/1901571-minimum-system-requirements-for-turbotax-windows-software

Minimum system requirements for Mac version:
https://ttlc.intuit.com/questions/1899173-minimum-system-requirements-for-turbotax-mac-software

The 2019 return cannot be efiled.  It will need to be printed, signed, dated, and mailed.  It's a good idea to mail by a method that has tracking, such as certified mail, priority mail, etc.

If you have both Federal and state returns, you need to mail each one separately to its respective tax agency.