CentOS have security measure to force users password expiration which can cause problems.
For example – you do not use passwords to log in to machines, and you prefer ssh keys. And the day the password for that user expires its cron jobs will stop working.
You can fix it with one of these, I prefer removing the expiration with chage:
chage -M -1 root
passwd -x -1 root
You can confirm with:
chage -l root