Environment: Red Hat Enterprise Linux Server release 6.6 (Santiago)
# crontab -e
Authentication token is no longer valid; new one required
You (root) are not allowed to access to (crontab) because of pam configuration.
# crontab -e
Authentication token is no longer valid; new one required
You (root) are not allowed to access to (crontab) because of pam configuration.
there were no changes in /etc/security/access.conf
the problem is root`s expired password
# chage -l root
Last password change : Mar 20, 2015
Password expires : Apr 29, 2015
Password inactive : never
Account expires : never
Minimum number of days between password change : 0
Maximum number of days between password change : 40
Number of days of warning before password expires : 7
# passwd root
and check
# crontab -l