If the Account Management Active Directory plug-in was configured to use non-standard port (other than 389) - the connection to Active Directory fail upon POA API methods execution.
The following error message appears in the poa.debug.log on the POA Management Node when the API method is being executed:
Unable to get LDAP entry for login (firstname.lastname@example.org). LDAP Exeption (-1 Can't contact LDAP server)
The problem is caused by the defect POA-82021.
The problem is going to be fixed in the future POA updates.