First try installing the device on a another computer.
If it also fails there, we can safely assume there is something wrong with your device.
Next, try to listen to the device. Does the harddisk make any small noise? Do you hear it spinning? If so, there is a big chance your harddisk is allright, but the electronic of the device is not ok.
Perhaps then you could try and dissasemble the device and install the bare harddisk in another device or just connect it straight to your (powered off of course) computer.