I faced the same issue, It seems to be catch issue. you have to delete the catch from database ADMIN_CONFIG table. I used Sqldeveloper to connect to the DB using admconfig user, take the backup of ADMIN_CONFIG table then if you find any rows with config_name LDAP delete it. Then try to login through client.
This trick work's for me. Now I am able to connect to P6 professional EPPM client.
You can review the below note on MOS
Error: "Invalid login name or password. Could not bind to object LDAP://<LDAP_Host>:<SSL_Port>/<Base_Directory_Node> (8007203A)" When Logging Into P6 Professional Configured For LDAP SSL (Doc ID 1439925.1)