From the manpage of crontab command:
If the cron.allow file exists, then you must be listed therein in order to be allowed to use this command. If the cron.allow file does not exist but the cron.deny file does exist, then you must not be listed in the cron.deny file in order to use this command.
So touching an empty file /etc/cron.allow can deny all non-root user to use crontab. Make sure that there is no empty /etc/cron.deny file present. This may create a conflict.
# touch /etc/cron.allow
To allow a user or some users to use crontab, append the user name(s) into the file and make sure one user per line, i.e allow user “test1” and “test2” to use crontab:
# echo "test1" > /etc/cron.allow # echo "test2" >> /etc/cron.allow
Verify the cron access by creating the crontab entry for the use :
# su - test1 $ crontab -e
# su - test2 $ crontab -e