Run the following commands to check the AD user account:
The account should be listed and the checkaccess should say allowed. If it says denied, check the access rules and check the account is not locked and the password is not expired.
3 - Crontab should have the sticky bit set. ls -l /usr/bin/crontab to check.
4 - Check the cron.allow file and the cron.deny file if they exist and ensure the rules are configured properly allowing access.
5 - Check the access.conf file if exist and ensure that the rules are configured correctly for access.
6 - Restart the crond daemon and then test again