The error encountered is

ORA-24247: network access denied by access control list (ACL)
ORA-06512: at "OWNER.LDAP_NTFY", line 410
ORA-06512: at line 2

And the solution is this:

column acl format a30
column host format a20
column principal format a20
column privilege format a10
column is_grant format a8
set lines 1000
select acl , host , lower_port , upper_port from DBA_NETWORK_ACLS; --# it looks that here we have ONLY the IP. In this case we need to add also the HOSTNAME
select acl , principal , privilege , is_grant from DBA_NETWORK_ACL_PRIVILEGES;
exec DBMS_NETWORK_ACL_ADMIN.ASSIGN_ACL('ACL_LDAPSYNC.xml','<hostname>',389,389);