cron is not working. You would see this error in /var/log/cron-* or /var/log/cron or in some configurations /var/log/messages. Its panic time!

Just kidding, bad file mode is just permissions.  You fix it with :

chmod 0644 /etc/cron.d/your.cron

Also a common one is WRONG FILE OWNER again rather straight forward :

chown root.root /etc/cron.d/your.cron

Note that you need root to be the owner, even tho you can execute it as a non root user.