I’m posting this in both the My Cloud and My Book forums as it is most likely to do with both.
I have just bought a My Book 8TB external hdd, thinking it would be just a matter of connecting it to the usb 3 port on my existing My Cloud. I connected it to my pc first and it ran a setup app on startup. Then when I connect it to the My Cloud, its not being recognised.
Check hte My Book for encryption. You (generally) cannot use an encrypted USB drive with the My Cloud (single bay).
As the previous poster indicated check the My Book drive format. The single bay My Cloud generally supports the following hard drive formats for attached USB drives: NTFS, HFS+, FAT32
Thanks for the replies and advice. After a couple of reboots and a lit of patience, the MyBook was eventually recognised, but then the MyCloud gave an error that a share couldn’t be created. But I could browse to the drive and use a script to map it as a network share. I’d like to be able to copy between drives using the dashboard, so I could shut my PC down when it’s working.