Sorry, but that cannot be done.
You can still file a 2017 return, but you cannot prepare it in Online
TurboTax, which is now for 2018 only. You have to use the 2017 desktop
software (CD/download.)
You can purchase 2017 desktop software as a download at this page and install it on your computer:
https://turbotax.intuit.com/personal-taxes/past-years-products/
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
Or
did you already start a 2017 return online prior to the 2017 online shutdown, and
want to finish that without starting over? If so, you can download the
*.tax2017 data file from your account and finish it in the desktop
software. If you already paid for your product previously, TurboTax
Support should furnish you the software.
The 2017 return cannot be
efiled. It will need to be printed, signed, dated, and mailed. It is
recommended to mail by a method that has tracking such as certified
return receipt, priority mail, etc.
If you have both Federal and state returns, you need to mail each one separately to its respective tax agency.
If you are due a Federal refund, it takes about 6 weeks for the IRS to process a mailed return.
Approximately 4 weeks from mailing, if you are due a refund, you can use this IRS tool to check on the status.
https://www.irs.gov/refunds
The current government shutdown may delay the timings mentioned above.
