The firmware upgrader software must be running alone on the network, with no CopperLan Manager running elsewhere.
There is a reason: the firmware upgrade tool and the CopperLan Manager are sharing the same exclusive resource (which is a CopperLan sub-protocol not related to the connections you can monitor in the CopperLan Manager). You MUST shut down the CopperLan Manager, AND THEN launch the firmware upgrader to make it able to see the device.