I purchased a 3TB My Book for Mac today, came home plugged it into my 2009 (OS 10.9.5 Mavericks) desktop and nothing happened. After hours of fiddling and googling, I called tech support, they had me download a driver from the WD website and it still didn’t work. They told me to return it for another. It was not showing up in disk utility or desktop icon. I plugged into my mac book pro, same thing.
So, back to the store I went. Exchanged, returned…same thing!
Are these drives USB 3.0? If so, I’d recommend trying a micro USB 2.0 cable. The connector for USB 3.0 may look proprietary, but it’s actually a s micro 2.0 with the USB 3.0 extension. As such, 2.0 cables fit in the “flat” portion:
The reason I recommend this is because several Mac computers from early 2013 and older have displayed specific compatibility issues with USB 3.0 devices resulting from Apple’s original refusal to adopt the standard.