I have set up a cronjob for root user in ubuntu environment as follows by typing crontab -e
crontab -e
34 11 * * * sh /srv/www/live/CronJobs/daily.sh 0
I experienced same problem where crons are not running. We fixed by changing permissions and owner by Crons made root owner as we had mentioned in crontab AND Cronjobs 644 permission given