This is a common issue with the SX-2xxx series of GDC server.  When the server is rebooted, the server hangs and doesn't load.  The most common cause of this issue is that a thumb drive was left in one of the USB ports.  When a thumb drive is in a USB port on boot, the server will first try to boot off of that drive.  Remove the thumb drive and do a reboot.  This can be accomplished by holding in the silver button on the front of the server.

If this doesn't work, a qualified person should attempt to use the built-in recovery console.