My CA return was rejected. It sates that the primary taxpayers SSN was already used in an accepted return. I verified it. and my SSN is correct. How should I proceed?

The error code you received indicates that the social security number entered for the primary taxpayer on the return has been used to file another tax return. Since this is the case you will need to print the California return, sign it, and file it by mail.  Please see How To Print & Mail A Return.