LDAP failed Diagnostics-Authentication

[fayRofa]

Hi,
1/on "SystemUser Manager>Authentication Servers" i add my ldap server;for my lab i used online LDAP server test(https://www.forumsys.com/tutorials/integration-how-to/ldap/online-ldap-test-server/):
Server: ldap.forumsys.com
Port: 389
Bind DN: cn=read-only-admin,dc=example,dc=com
Bind Password: password
2/on "SystemUser Manager>Settings" i tested my ldap server all are ok(you can see the attached imag)
3/Doing test via Diagnostics->Authentication, I don't get anything ;Authentication failed, for an existing user/pw at the LDAP server?
and no error massage found in system>logs file?
please do you have any idea about this error?
Thank you.