To reboot the server via Plesk Control Panel
1) Login into your your server via Admin Page
2) From Home page, click on TOOLS & SETTINGS (Left Panel)
3) Under SERVER MANAGEMENT, click on RESTART SERVER to reboot
4) Click OK to the prompt Window to confirm.
Note: This will initiate the reboot of your server. Please wait for about 3 to 5 minutes to re-access your server after the rebooting process.