How to reboot my vps if I can't ssh login?

You can find your vps at menu "Service"->"My Servers" after login ComfortVPS client area. 

Directly Link: http://www.comfortvps.com/clients/clientarea.php?action=products

Then click the "View Details" to see the bandwidth usage and control your vps such as reboot / shutdown.

 

 

Tutorial: