NT authentication method requires setting up a Windows user account to run the QPR service. The user account you are using to run QPR Service must have "Logon as service" local security policy rights on the computer where the service is executed. Otherwise it is not possible to use group synchronization with NT authentication in the User Management System.
Note that currently a secure LDAP authentication requiring a client certificate is not supported. However, it is still possible to secure the connection to the LDAP server using SSL.