A bit of googling showed that it seems to be a clock signal that old keyboards don't bother with. Not sure if this clock signal is sent, or how practical it would be to add it to the firmware(s).
Actually, the other solution in that post stream is to install the Realtek drivers, as they aren't part of El Capitan. This is why the turtle doesn't show up.
Once you know which interface is the Lan Turtle (if in doubt, unplug it, run ifconfig as above, replug and run ifconfig again, new interface is the Turtle) run dhclient (or Mac Equivalent) on the interface. Failing that, give it a static IP of 172.16.84.5 (netmask 255.255.255.0) and try again.
The turtle did have issues with load drivers for certain versions of OSX. Can you post the following extra info:
What version of OSX you are running.
Example output from ifconfig / ipconfig / whatever OSX uses and an indication which adapter is the turtle.
Can you ping the turtle?
Have you tried plugging in the turtle via the ethernet cable to the laptop you are trying to access it from?
p0f does passive fingerprinting. So the windows 10 machine would need to generate the traffic.
Also, you might want to try some of the other scan types such as Xmas tree and Fin. You could also try the nmap man page, and go through each can type to see if anything gives a better result.
Bear in mind, that sometimes firewalls are completely closed off and another avenue is required.