If one does a forum search via the magnifying glass icon upper right they’d see that trying to sync the contents of one computer to multiple other computers through the My Cloud using WD Sync can be a hit or miss affair. Sometimes it works, sometimes it doesn’t. Some has speculated that when it fails its because two or more computers are trying to sync to the same folder on the My Cloud which causes WD Sync to fail.
One would need to direct WD Sync on each computer to use the same folder on the My Cloud so that all synced data is stored in one single location on the My Cloud.
One might have better luck, if all computers are on the same local network, using a third party sync program like Free File Sync (http://www.freefilesync.org/).
Here are a few past threads on the issue when using WD Sync.
https://community.wd.com/t/wd-mycloud-sync-issues-between-2-computers-and-cloud/159292
https://community.wd.com/t/wd-sync-not-syncing-between-2-computers/141218
https://community.wd.com/t/sync-between-folders-on-different-pcs/149985
https://community.wd.com/t/how-to-sync-two-mycloud-at-different-locations/145528
https://community.wd.com/t/syncing-folders-on-wd-mycloud/95486
