If you have a 2019 taxfile then you would need 2019 software to open it.
That's what I was thinking. But when I went to my Turbo Tax account online and tried to pull up the Turbo Tax 2019 program to reinstall it, it didn't appear in my list of products...
I assume you did use the Desktop program for 2019? And you have the .tax2019 file? How did you originally install it? From the CD or the download? Did you buy it from Turbo Tax or somewhere else?
If you bought the download from Turbo Tax, It's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
https://myturbotax.intuit.com/account-recovery/