Problem scenario
You have modified the crontab (e.g., with sudo crontab -e), but the job is not running. What can you do?
Possible Solution #1
A good troubleshooting technique of a cronjob is to configure it to have this job * * * * * env > /tmp/list.txt. You then analyze /tmp/list.txt to see if it is different from the results of running "env" manually. If the results are quite different you may want to consider using Ansible. It can be easier to use Ansible to configure a cron job. Ansible's supported cron module may work more reliably.
To install and configure it, see this link if you are using CentOS/RHEL/Fedora, and this link if you are using SUSE.
Possible Solution #2
You may want to this this posting on Serverfault.com.
Possible Solution #3
This external site may help you.
Possible Solution #4
This site crontab.guru could also help. It is a very good reference.
Possible Solution #5
To get the crontab job to execute as a human thinks it should, you may want to see this continualintegration.com posting. The problem may be both temporal and related to a triggering event.