My Book Duo Won't Mount on Mac

Brand New ExFat Formatted WD My Book Duo (16 Tb- 2 x 8 TB) will not mount on late 2012 MacBook Pro Retina running OS Sierra (version 10.12.2).

The Drive appears in the following locations:
System Report>USB and Disk Utilities (where it is grey) but will not mount. Clicking the Mount icon in Disk Utilities would not mount it.

I had an identical WD My Book Duo (brand new, with similar volume of data but different data, 16 TB, etc) which also would not mount on this computer. It would mount on some PC’s but not all PC’s running same Windows OS (I believe 7 but am not at work to verify).

Any recommendations would be greatly appreciated. Thank you.


Does the drive works on a different system?

Have you tried reformatting the drive to HFS+ ?

The drive mounts on a Windows 7 OS. I can’t reformat HFS+ without losing the almost 16 TB of data on it.