can u check by creating a user id and login using ssh.Also check the user details in /etc/passwd and /etc/shadow file.It may be having some issue with min time period in /etc/shadow or expiry of account.
One more way u can check is create an account using the syntax
useradd -e expirydate
so that you can confirm that expiry is happening on that date.
For more info check man useradd