When CL3000N get into the firmware upgrade mode by dip switch, but upgrade fail. 

Please try to get into the firmware upgrade mode by hot key ([Ctrl] + [Alt] + [Shift] + [u] + [p] + [g] + [r] + [a] + [d] + [e] + [Enter]), then try upgrading firmware again.

Note: This Hotkey sequence only works when the firmware upgrade switch  is in the Normal position.

If you still have problems, please contact ATEN Tech Support.