There seems to be a flaw in the MyCloud firmware design that allows it to run out of disk space, which renders the operating system unusable. It’s possible that a 4-second reset will clear enough temporary swap space to allow you to regain access. I thought I’d seen previous reports of this problem, but I can’t find any with the obvious search strings…
If not, then you may have to resort to removing the disk from the enclosure, and recover the data, or make some space.
