It can happen that the NIC is not being started while the software already is. You can restart it from the command line. If that works and you get it more often you can add the fix to the software. 

First boot the software, then type  exit somewhere in the software, a popup as below will appear:

Please confirm you would like to leave to the command line.

In the command line you type /etc/init.d/network restart   and see if it obtained an IP

If so you know the NIC is supported but just could not get activated on time. This might happen if the machine is connected to a Moden w/o a switch or some other rare cases. 

Now you can type wd_ui to get back to the software, DO NOT type exit as this will reload the software. 

If you're booting from USB and need a permanent fix you can use the file: sample-network.cfg, rename it network.cfg and change the line: dhcp_args="--retries 2 --timeout 30" 

Example: dhcp_args=--retries 3 --timeout 20

Drop this network.cfg file to the USB and it will now restart the NIC if it fails the 2nd time. 

DO NOT use the network.cfg file in combination with the PXE server