Did you try to execute the following actions from command line prompt? If not, do so..
cd %plesk_bin%
Parallels.MonitorSrv.exe --update-config
php.exe -dauto_prepend_file= "c:\program files (x86)\parallels\plesk\admin\plib\scripts\setup-health-monitor.php"
Then restart the Health monitor service..
Regards,
Sujith