TurboTax cannot be used to prepare or file a stand alone state return. The information flows from the federal return to the state return. If you used TurboTax to prepare your 2018 federal return then you can download the 2018 desktop software and then prepare the 2018 CA return. Or you can get the state forms from the state site and prepare them by hand.
https://ttlc.intuit.com/questions/1900990-how-do-i-file-a-prior-year-tax-return
https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/0...
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