Why am I unable to report on the ratings given within a completed performance document?

I need to be able to report on the ratings given by the manager for a pre-assigned performance document.

I am using the Workforce Management - Performance Rating Real time subject area in OTBI, which returns the name of the document, however when adding any field from worker folder (such as person number, name) it then returns the no results error message. However I can see that in front end there are at least 2 employees who have had ratings given and the document is completed so I therefore expect that I should be able to report on these employees.

Please can anyone shed light on why this is happening