You may not be able to view all user if you have selected the Primary department.  If the user/employee is added in the Sub-Department you'll have to select that department to view his profile.  

 
Please follow the steps below to resolve the issue.

 
–  Login with Administrator privileges.
 
–  Click on Users.
 
–  Check Include Sub-department to view users of all Department.
 
Note : The above mentioned steps may not resolve the issue if 'Hierarchy Filtering' is enabled on the application.