you don't need to restart anything. Every minute the file is read and if a change is made then crond will reload this. The only thing ist: crond must be running - of course.

So, after max 2 minutes the new cron file should work.

You should see in the syslog (or /var/log/user ???) if the crons are running.

What's not ok so far?

Sorry, I forgot to copy it to /etc/cron.d/ispcp