How was the connectivity between 2 tested?

What's you setting looks like?

Is port 369 opened?

There multiple thing that play the role.

You may check the user guide to setup LDAP.

We are using port 636 and I tested the LDAP connectivity between ALM server and LDAP server, it is opened and working. But when I try to connect from ALM Site Admin it is not working. I followed this document community.microfocus.com/.../qc-alm-support-tip-how-to-enable-ldap-over-ssl-for-qc-alm.

I mean to say 389 but you already said you are using custom port.. Does your telnet looks good to?

If its ok, share your setup hiding or changing sensitive info

Yes, tested the connectivity with telnet and it worked.  Please see the attached screenshot regarding setup and test results from ALM Siteadmin UI.

Do not have much info from the screenshot. Was expecting to see error detail as well.

Have you deployed SSL certificate in ALM Server?

You can use LDAP tool, such as https://www.ldapadministrator.com/softerra-ldap-browser.htm to test your connection string and data before configure in alm. In addition, follow the guide. https://admhelp.microfocus.com/alm/en/16.00-16.0.1/online_help/Content/sa_users_import_LDAP_SSL.htm