Does User Signoff Report work in Agile 9.3.1.1
This sounds like a call to support. Is this a new instance or an upgrade? Test system or production? Have the services been recently restarted?
As of now, the User Signoff Duration report does not support QCR and PSR objects. Oracle have an Enhancement request open for it. it will be incorporated in a future release.
But if you are trying for other objects, it should work.
Check one more thing, if workflow statuses or name has any special characters..