You are correct, this reject is when the spouse's SSN in the return must not be the same as the Primary SSN on another return filed for the same tax year.
You should verify that the information is correct, name, SSN, date of birth, if there is a correction needed do it and resubmit. If everything is correct, you will have to contact the IRS for further guidance and file by mail.
It would be recommended to file a report of identity theft.