1. Log into the Customer Control Panel with your main account's username and password.
2. Click on the "Websites" tab.
3. Click on the "Domain" in question.
4. Click on "Web Hosting Settings" link.
5. At the bottom of the page you'll see a "Stop" button, click the button to stop the site.
6. Then you'll see a "Start" button, click it to start your site.
You've successfully restarted your site.