The key with my D-Link DIR-655 to locate the current network WPA Key is to follow the menu items necessary to add a wireless device to the already set up wireless network. Probably there are other menu navigation methods, but the one that recently worked for me follows:
Display Current Wireless Settings [Find WPA Key]
1. LOG IN to D-Link DIR-655 via default IP address 192.168.0.1
2. click “ADVANCED” [top panel]
3. click “WI-FI PROTECTED SETUP” [left panel]
4. click “ADD WIRELESS DEVICE with WPS”
5. click “MANUAL” to display the current wireless settings.