OTBI report is not working for few employees

We have an OTBI custom report that retrieves absence details without applying any filter conditions. The report uses the following subject areas:

• Workforce Management – Absence Real Time
• Workforce Management – Absence Calendar Details Real Time
• Workforce Management – Worker Assignment Real Time

When we run the report without passing a person number, some active and inactive employees do not appear in the output.
However, when we explicitly enter the person number, the absence data for those same employees is returned correctly.

Can you please advise what might be causing this behavior?
Is there any internal filtering, data security, or assignment-status logic within these subject areas that would exclude certain employees when no person number is passed, but include them when the person number is explicitly specified?