You should check if your computer is detecting that the scanner is connected.
If you are using a PC go the start menu→ control panel→ system→hardware→ device manager: All the connected devices will be listed.There should be one called imaging device or Nikon (scanner model). If there is a ! symbol, this means the device is not working properly, due to a possible problem with drivers. Try reinstalling the drivers.
If the device is listed without the symbol above, then it could be a software fault. Check the Nikon website for the latest software for your scanner and operating system. Completely uninstall existing software and re-install.
If the scanner is not listed in device manager, then it is probably not initializing properly due to internal hardware errors, or the USB/Firewire port may be faulty. If this is the case, contact Camera Clinic to book in for repair.