If it's greyed out then its either not got any power to it, it isn't connected to the hub by any means or it's died.
Many older NAS, including yours, will not connect unless SMB 1.0/CIFS is activated, but in Win 10 this feature is deactivated by default. You can check this in 'Turn Windows features on or off' . If it needs selecting then also select SMB Direct and reboot.
Just a thought, have a look at My Network again and make a note of the MAC address (the one that goes something along the lines of 1a:2b:3c: etc) against the greyed out device and see if there is an new Unknown device with the same MAC code and is highlighted in green. It's possible that the IP address has changed and the one you're looking at is no longer valid .
Or simply open a Windows explorer window (not a browser window) and type \\wdmycloud in the address bar
Thank you for the suggestion. I have found how to do this, turned the settings on, rebooted and gone through a reconnect process for the cloud.
Nothing changed. Now about to reboot having changed said settings back.
Much appreciated though.
Do you, or does anyone you know have a spare or disused router? It would only need the LAN side to work but by connecting both NAS and your computer to it and giving both fixed IPs in the same subnet, say 192.168.1.1 and 192.168.1.2, hopefully you would be able to access the NAS from your computer and grab what you want. If you still can't access it then it's u/s.
The \\wdmycloud option would give you access to your files through Windows Explorer providing that your PC and my cloud device are on the same network. For this reason I think you need to check power to the WD device and the ethernet cable between it and your hub.
Can you see any lights on the WD device? Could it be something simple like the my cloud having been accidently switched off on the device itself?