In the Network Settings utility, did you press the “List devices” button? That should list the network settings for all SM200Cs that are connected to the PC.
Do you happen to have a windows PC you could install Spike on and try the USB config?
I definitely trust that the Windows implementation of the USB network config to work 100%. When plugged in via USB to a Windows PC, it should also show up in the device manager as an SM200C in the Universal serial bus controllers tab in Windows (as long as you have installed Spike which installs the USB driver for the SM200C).
If on Windows you also get the device not found message in the network config dialog, or it’s not showing up in the device manager, it could be hardware failure.
When connecting in Spike, it should be toggling red/green on a ~1 second cycle, so definitely something not right.
If none of the above helps, email aj@signalhound.com and we can determine the next step. We might have to dig deeper into the FW and what might be happening.