If you haven’t done so already, you may want to see a similar discussion to see if there is anything discussed in there that could help your situation:
What does “falling off the network” actually mean? Is the device no longer listed in the router’s DHCP client list (usually found on the router’s administration page)? Is the My Cloud no longer reachable by it’s IP address? Can you reach the My Cloud Dashboard using a web browser? What color is the front LED? Are you using a single bay/single drive My Cloud or some other multi bay model? Note the My Cloud Home is a completely different device with different features and options.
As a troubleshooting step, have you tried putting a network switch between the My Cloud and the network router? In certain rare cases there is a conflict between certain ISP provided routers and the My Cloud.
My Cloud is not recognized when connected to AT&T Uverse, Pace, Arris, Ubee or Sonic Gateway Routers
Also note that if using Windows 10, ensure SMB1.0/CIFS is enabled since Microsoft typically disables that option in recent Windows 10 updates (or in new installs of Windows 10).
How to Enable SMB 1.0/CIFS File Sharing Support on Windows 10
