Connecting LDAP return [LdapNetworkConnection] null

Hi all,
i trying to use LDAP for authentication in Graylog but i received always this error in file /var/log/graylog-server/server.log

https://paste.fedoraproject.org/paste/U7zSUzBn9Gqeb7AnwmzU9Q

in web interface it say: Connection to server was successful

ā€œbinding with user nullā€ makes me wonder what your LDAP settings are… maybe post them?