In order to test LDAP connectivity and make sure it is working fine, I've tested the following command on my CentOS server where OSTicket is running:
ldapsearch -x -D "CN=userID,OU=USERS,OU=WLON01 London,OU=England,OU=Europe Africa and Middle East,DC=level5,DC=level4,DC=level3,DC=com,DC=br" -W -H ldaps://nononono.nonono.nonono.com.br:636 -b "OU=England,OU=Europe Africa and Middle East,DC=level5,DC=level4,DC=level3,DC=com,DC=br" -s sub 'cn=userID
After typing the correct password, the query succeeded. Grateful in advance for any hint.

Done! https://forum.osticket.com/d/96963-error-trying-to-use-ldap-authentication-using-tls-port-636

Hello everyone,
I've being using standard LDAP authentication over a Microsoft domain, via port 389. It works flawlessly. Now we're moving to a more secure approach, enabling TLS and authenticating on port 636. So I've put ':636' in the end of all server names, and enabled the TLS, as shown in the image below:

Now I'm receiving the error message "Could not connect to xxxxxxx.com.br:636:389: Unable to bind to server xxxxxxx.com.br:636"
I've tested ports 389 and 636 and both are available through firewall, so there are no connectivity issues.
Any help would be much appreciated.

Hello everyone, I'm having the same issue described by @kristo993. Here's the error I'm receiving while configuring LDAP authentication plugin:

Any hellp would be much appreciated.