Have you looked through /var/log/auth.log to see what the specific error is?
(sudo tail /var/log/auth.log -n 20)
I'm not sure how your user authentication system is set up, but it could also be a pam issue. Check /etc/pam.d/ssh to see if the relevant authentication system is set (pam_unix.so for /etc/{passwd,shadow}, pam_ldap.so for LDAPs, etc.)
Without more details, not sure where else to point you towards. Generally auth.log would be a good start to see what error is being thrown.
How were you logging in before?
Cheers,
-s