The TurboTax online editions for tax year 2018 have permanently closed. The TurboTax online edition for tax year 2019 will be available in early December.
If you need to complete and file a 2018 tax return then you will need to purchase, download and install on a personal computer, Win or Mac, one of the TurboTax desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2018 tax return can only be printed and mailed, it cannot be e-filed.
remember that the efiling deadline for a 1040 is generally 10/15 of the following year. after that date, if the return is complete, you must print and mail. if it's not complete you'll have to buy the desktop software to complete and mail. also if you want a complete copy of your return (including worksheets), you should save a copy as a PDF. during the period that TT is converting from 1 year to the next, you may only be able to print those forms required for filing. printing of worksheets and other feature will be unavailable,