Online should be closed now to start a new 2018 return. Yesterday Oct 15 was the last day to efile. You need to buy the 2018 Desktop Download to do 2018 now. Currently it is still listed on this page,
https://turbotax.intuit.com/personal-taxes/cd-download/
But soon it will move to the prior year products page here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
