In addition to rac8006’s suggestion to read the Firmware 4.05.00-315 discussion thread, also use the forum search feature (magnifying glass icon upper right) to search for the many past discussions on the sleep issue with the My Cloud units. There is MUCH discussion on various methods to try in order to get the unit to sleep for more than 20 or 30 minutes along with discussion on the various causes for the constant wake ups.
https://community.wd.com/t/firmware-4-05-00-315-discussion/202234/
Generally the My Cloud (v4.x units at least) are set to go to sleep after 10 minutes of inactivity. Problem is certain services on the My Cloud trigger disk activity every few minutes to every 20 or 30 minutes keeping the My Cloud awake. Making matters worse is local computers/devices on the network may also “tickle” the My Cloud keeping it awake even though no files/data is being accessed on the My Cloud. For example in my case bringing a Windows 10 PC out of sleep/hibernation often causes the My Cloud to wake up.
