You should start a new account instead of trying to use an old account that was used for joint returns in the past. It is too hard to remove all the embedded "spouse" stuff from the old account. Start a new account with a new user ID to file Single.
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-onli...
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
