There are many past discussions on this shutdown issue that affects the second generation single bay My Cloud units. WD has known about the many complaints both in this subforum and in the Cloud Ideas subforum for years but for what ever reason WD will not re-enable the shutdown option in the My Cloud Dashboard for the V2.x single bay My Cloud.
The workarounds to this issue are to use the WD recommended method for shutting down the My Cloud using the WD Quick View program. Or use a web browser hack to trigger the hidden shutdown button on the My Cloud Dashboard. Or to use SSH to issue the shutdown command. By using SSH one may be able to setup a script on their computer to issue the command when that script is run.