Manager ID not available in Manage Users

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Manager ID not available in Manage Users

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Hello Friends, I am trying to update Manager for a user through Financials >> Manage User >> Update Manager using the list of values. However, the manager id is not available neither in test nor Production.

Several AP invoices were still routed to the inactive manager, and I was not able to replace it for the new one.

Any idea why the manager id is not available. All the attributes for both the user and the manager seems to be fine.

I noticed the only difference between the previous and new manager is the name and start date.