Recently after installing a fresh new copy of Debian 10 (Buster), I found that root ssh access was set to without-password by default now. What that means to you is that if you are trying to ssh to your server with your root account and password, you will receive an access denied error. In order to overcome this limitation, you will need to edit the file /etc/ssh/sshd_config to allow root password logins through ssh. As shown below, comment out #PermitRootLogin without-password and add PermitRootLogin yes.
# Authentication: LoginGraceTime 30s #PermitRootLogin without-password PermitRootLogin yes StrictModes yes
Once the file is saved, you will need to restart the ssh daemon in order for the changes to take affect using the command below.
service ssh restart
After the ssh service is restarted, you should now be able to login through ssh using your root account and password.
It would be nice if you could also write about why the password login for root is disabled by default, and how one can instead use ssh keys to log in as root. Or use sudo.