Ensure both the My Cloud and your computer have the latest updates.
If using Windows 10 there are known issues with the Windows 10 November update with the My Cloud including the My Cloud not showing up properly under Windows File Explorer. Microsoft released a Windows 10 Update this past Tuesday (March 1, 2016) that appears to fix the My Cloud / Windows 10 File Explorer issue.
https://community.wd.com/t/windows-10-kb-3140743-possible-fix-for-my-cloud-issue/153567
https://community.wd.com/t/compilation-of-windows-10-methods-steps-and-solutions/142576
