Compensation plan - employee's manager can't see his report after customizing hierarchy

Content (please ensure you mask any confidential information):

Hi all,

we have an employee who has his organizational data empty. this is a particular status of some employees for our client (stato secondario= Congedo straordinario)

Now, this employee should be visible in a compensation plan so from My Client Group > Compensation > Administer Workers > Employee > Compensation plan > Status and hierarchy, we customized the hierarchy adding a manager.

But the manager, from My team > Workforce Compensation > Compensation task, can't see the employee from his reports.
this doesn't happen if the employee to whom we customize the hierarchy has all the organizational data filled.