Use the link below.   Bookmark it for handy future use.   At the page do not click the "Sign In"  link in the top right corner; that's for TurboTax.

Instead click the link in the center "Start Itsdeductible"--even if a returning user.

https://turbotax.intuit.com/personal-taxes/itsdeductible/

If you have been clicking "Start ItsDeductible", but it's opening your Online TurboTax account, then log out of everything.  Empty your browser Internet cache and any Intuit-related cookies.  Close the browser and reopen it, then go to the link above and choose "Start ItsDeductible."   It should then ask you to log in.

If problem recurs, then try using "private browsing"; i.e., a private browser window.  Or try a different browser if you have one.