This happens if you not executing the cron job under root. Only root executes the CRON jobs mentioned under crontab. To execute your own script for testing, just create your own user ID under cron directory(Crontab). Then, write a fresh crontab -e script and execute it manually.

Else, you need to put this command under the crontab file, which executes automatically by root. Also, check if you are getting any error message in the *.err file.

Thanks,
Rohit..