I found alot of topics regarding this problem, but all of them are older then a year.
My Cloud 4 TB which I just bought yesterday, does not go into energy saving mode. In my opinion the HDD spinning is cleary audible, and the LED is blue. Nothing changed in 8 hours of doing nothing.
My settings:
Cloud Access (Remote Access and USB Content Availability) both turned off
Energy Saver (Drive Sleep and LED) both turned on
Mac Backups TIme Machine turned off
Language and Clock NTP-Service turned on
Network Mode DHCP
Media Streaming turned ON
iTunes Server turned off.
Firmware (Up-to-date): v04.04.01-112. Last update. 2015/12/12 9 PM
I mapped a network drive on my PC. And I got a WDTV on my network.
Everything was turned off - except MyCloud, and MyCloud didn't went into sleep mode. Any idea/fix for this?