The Service Account DN is the distinguished name of the user account in LDAP which will be used to make an authenticated bind to the LDAP server. You need to give the Distinguished Name attribute value of any user account for the Service Account DN field in the plugin and password of that LDAP user account.
1. Check if you have entered valid Service Account DN (distinguished Name) of the LDAP server.
You can also give the userPrinicipalName value of the LDAP user.
2. Check if you have entered correct Password for the Service Account.