my ssh has started to refuse users from out of the blue. I started to connect via Putty as root, me and other users.
login as: root root@31.XX.XX.XXX's password: Access denied
What could be wrong? I didn't change anything.
By default root user is not allowed to login in SSH remote connection. Anyway I recommend you using a normal user to work, not root. You can always use sudo if you need it.