you need to have the Ethernet adapter that you are using configured with the correct IP Range. You can check the IP of the Pkanet Board in the "Set Parameters" for the controller (in the Machine Menue)
Choose a IP in the same range and enter the IP of the Adapter that you are using in the Settings Menu as "Adapter IP"
Closing and reopening of the Settings Menu might be required to make the board visible after setting the Adapter IP.