I have the same issue.  The SSN requirement of the Officer signing the return is new on the ProSeries 2020 Form 990 Information Worksheet Part VI.    Obviously my client (the officer of the nonprofit 501(c)(3) is not wiling to give me his SSN because the 990 is public information and is readily accessible to the public with 2 clicks on the EO search tool at irs.gov.    The IRS instructions say nothing about this new requirement.   If I leave it blank, the box is highlighted "pink" as an error.     Is there a "workaround" that Proseries has so I can efile the 990 without entering the officer's SSN?