Don't think you can efile a business return for 2018 anymore. Maybe from a local CPA. Why are you trying to buy the program? You should have it from doing the Federal. Did you use Turbo Tax to do the federal 1120S? If you didn't use Turbo Tax then you can't use Turbo Tax to do the state.
You can buy 2018 from here
https://turbotax.intuit.com/personal-taxes/past-years-products/
