How is the My Book drive formatted? NTFS, FAT32, other?
In certain instances some of us (me included) have experienced problems with the My Cloud not properly mounting an external USB hard drive. In my case it was a 1TB Toshiba Canvio USB hard drive. The work around in my case was, using Windows 7, to delete all the partitions on that USB drive, then repartition that hard drive with one single partition, then reformat the drive to NTFS. Then the My Cloud would properly mount the drive. I detail some of my experiences in the following post (and discussion):
https://community.wd.com/t/this-is-absolutely-unacceptable/149432/23
