Then either the physical drive in the enclosure or the enclosures electronics has failed.
WD is known for using lousy electronics in their external drives so the actual drive inside the enclosure is probably still ok. The only way to tell is to crack open the enclosure and extract the drive then use a SATA to USB adapter, one that has its own AC power supply, to connect the drive to your Mac.
SATA card failure, extremely common
all about same here:
ba1010 wrote:I don't think it's the cord because......
it almost never is the USB cable. Its absurdly rare.