I have my daughter as dependent. She got married last year and her husband list her SSN on his tax return as Married File Separate. He did not claim her but said that they required to list her SSN in his return.
Yes, he is correct that the IRS requires the SSN to still be listed on the return for MFS purposes. Unfortunately, due to the heightened security measures the IRS has in place for SSN matching and e-file, you will need to paper file your return to claim her as a dependent. The e-file system is going to continue to reject your return, but it will be processed if you paper file.