If the cron service on your MacBook has stopped working, here are some steps you can take to troubleshoot the issue:

• Check the status of the cron service: Use the ps command to check if the cron service is running. Type ps aux | grep cron in the terminal to see if the cron service is currently running. If it's not running, you may need to start it manually.
• Check the cron logs: The cron service logs its activities to a file. To view the cron logs, type tail -f /var/log/syslog in the terminal. This will show you the last few lines of the system log in real-time. Look for any messages related to cron, such as errors or warnings.
• Check the crontab file: The crontab file is a configuration file that tells the cron service what jobs to run and when. Type crontab -l in the terminal to view the contents of your crontab file. Make sure that the syntax of your cron job entries is correct, and that they are scheduled to run at the correct times.
• Check the permissions of the cron files: Make sure that the cron files have the correct permissions. Type ls -l /usr/sbin/cron in the terminal to view the permissions of the cron binary. It should have the permissions -rwxr-xr-x (read, write, execute for the owner; read and execute for group and others). Similarly, check the permissions of the crontab files by typing ls -l /usr/lib/cron/tabs.
• Restart the cron service: If none of the above steps resolve the issue,
  you may need to restart the cron service. Type sudo launchctl unload /System/Library/LaunchDaemons/com.vix.cron.plist to stop the cron service, and then type sudo launchctl load /System/Library/LaunchDaemons/com.vix.cron.plist to start it again.