The steps I’m suggesting will work on a Mac, too. Just a little differently. Instead of putty, you would just open a terminal window (Finder - Applications - Utilities - Terminal) and then type SSH, but I think we can check this a little more easily using the NAS web UI.
Are you using a static IP address for the NAS? If so, have a look at network setup in the NAS web UI => Basic Mode - Network page. Even if you aren’t, the “Default Gateway” and “DNS Servers” will be shown. They will just be “dimmed” so that you cannot change them. On a Windows pc, these should be the same as shown in response to an “ipconfig /all” command in a DOS window. For Mac, look at System Preferences - Network - Ethernet (assuming you are using a wired connection, otherwise select Airport). The entries in the NAS web UI for “DNS Servers” and “Default Gateway” (“Router” in Mac System Preferences) must match your computer’s settings.
As another check, can you try “ping websupport.wdc.com” from your computer? In Windows, this is done in a DOS command window. On a Mac, open a Terminal window and enter the command. In Windows, ping will stop after sending four packets. On a Mac, “ctrl-c” will stop it.
Let me know what these steps show and we’ll decide what’s next.