If the cron jobs execute correctly, you will have logs in the backend > misc > cron jobs history. If you don't have logs there. the cron jobs don't run.
You can add here a screenshot with the way you added the cron jobs in plesk, maybe we can help.
Most likely you're not using the right PHP binary, plesk defaults to php 5.4, so you should not use /usr/bin/php in command line for crons, but something like /opt/plesk/php/7.4/bin/php