I found that the configuration software which came on a CD with the adapters is incompatible with Windows 8 and the product itself is out of production.
After messing around unsuccessfully with the old software in a Windows XP VM in VirtualBox, what eventually worked was much simpler. With a firmware upgrade on the adapters and a newer configuration utility which installs on Windows 8, I was able to configure the adapters to talk to each other.
- Download the last available firmware for the dLAN 200 AV powerline from the Devolo site: http://www.devolo.com/en/Downloads/dLAN-200-AV
- With a powerline adapter directly connected to the PC, double click the firmware exe. It launches and installs the firmware successfully.
- Repeat for the other adapter(s).
- Download and install the dLAN Cockpit utility from the Devolo site: http://www.devolo.com/en/Downloads/dLAN-200-AV-Wireless-N
- Connect one adapter direct to the Windows PC, the other to the router.
- Launch the Cockpit utility
- Click Options and select Reset network to factory defaults
- Click Add adapter and enter the security ID of the adapter connected to the router
After a short wait, the second adapter appeared in the Cockpit UI showing connected.