employee missing in hiring manager drop down

Summary:

employee missing in hiring manager drop down

Content (please ensure you mask any confidential information):

We notice an issue where one of the employee is missing from the Hiring Manager Drop Down list. We can see all other employees with similar roles are visible in the drop down even other without the role but somehow this one employee is missing in the drop down of hiring manager while creating the job requisition.

So far we tried deleting the user and recreating the user considering some user issue but didn't work.

What is the logic behind this Hiring Manager drop down field on Job requisition??