Some Users cannot see Leavers despite Correct Roles

Content

Hi all, got a weird one! 

I developed some leavers reports a few months ago and they worked perfectly for me and for users when they tested them. The report is nothing out of the ordinary, just a leavers report with the employee's details and termination dates. 

One of our HR Leaders left our company and the HR Reporting Analyst could not see them on their leavers report, despite having the Human Resources Analyst + Specialist View All roles and all the correct Areas of Responsibility. We never investigated this further as it didn't occur again. The issue got re-raised when another senior member from HR left and the Reporting Analyst couldn't see her appear on the report either.