Root login not working in Linux Mint login interface

Hello members

I would like to enable root login as i have set in the screen shot below, but when i reboot the machine and try to login again, the root login does not work.

What could be wrong and how can i solve this. Thanks in advance for helping.

Did you assigned password for root user after enabling allow root user and also once look at the conf file mdm.conf what was configured there.

#sudo passwd root

#vim /etc/mdm/mdm.conf