Downloaded 2018 .tax file isn't recognized...

I am trying to file my 2019 return through the desktop TurboTax software (as it's no longer available online at this point). I've purchased the TT 2019 software and I received my 2018 .TAX file that TT emailed to me in a zip file which I extracted.  When I start my 2019 return, it doesn't recognize the downloaded 2018 files even though it's in the TurboTax folder.  What am I doing wrong?