You need to have the 2017 and 2018 tax program installed to prepare prior year returns.  Yes, both 2017 and 2018 can still be Efiled.

Log into your Intuit online account and see if prior year programs are available for you to download, if not, you'll need to call support.

https://www.intuit.com/sign-in/   Scroll down to ProSeries and Log in.