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.