Jeremy Davis's picture

Root login should work in Webmin, Webshell, SSH and SFTP. If you are trying to login to the WebUI of a specific webapp (e.g. WrodPress, Joomla, Drupal, etc) then root will not work. You'll need to use whatever admin account is relevant to the specific app (see the relevant appliance page for details, generally it will either be 'admin' or email address configured on firstboot).

Just having reread your post however it sounds like you are trying to log in via SSH (or local terminal). Is that right? Depending on where the system is running you may be able to reset the root password. If you can get access to a local terminal during boot then this should help (Proxmox is Debian based, same as TurnKey).