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:
Or download blank forms from the IRS and fill them out by hand for free.
How to finish a return you started online
To do a prior year return you have to buy the Desktop program here,
You will need a full Windows or Mac to install it on.
Or If you have a simple return You can fill out the blank forms for free.
Here is the IRS 2018 Form 1040
And instructions https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf
2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf
IRS 2018 Schedules 1 thru 6 (only if needed)
Don’t forget your state. And you will have to print and mail your returns. So be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.