That little black button is the reset button. This also resets the IP address. It will now either be on 192.168.1.99 or 192.168.2.99 depending on your firmware version.
I have tried both IPs and done an IP scan. Nothing is showing up on my DHCP table either.
You can see the network light flashing, hook it up toa PC with a packet sniffer like WireShark and see what's coming out of that network cable.