Urgent help: centos6.2 system, ssh not available, show Accessdenied, do not connect to the monitor, dellR710

Urgent help: centos6.2 system. ssh is not supported. Accessdenied is displayed, and display is not displayed. dellR710-Linux general technology-Linux technology and application information is displayed. For more information, see the following. A dell server in the company suddenly fails to log on via ssh. ftp is normal, and Access denied is prompted when you log on with putty. a wrong password is displayed when you log on with CRT, but the password is absolutely correct, then I connected the monitor to the machine room. the monitor could not be displayed, but the monitor could display the process when I turned it off. then I logged in with a single user, and the monitor could display the display. I went in and changed the password, I checked the sshd_config configuration file, and so on. firewall and selinux are all off. in single-user mode, Port ftp, sshd, 21, and 22 are all enabled, the test shows that ftp can be used normally, but ssh cannot be connected, root and common users cannot be connected, and reboot can be started normally after reboot. it's still the same, so I am in a hurry to ask for help ~~