First troubleshooting step (requires local network access to the My Cloud) is to turn off remote access/cloud access in the My Cloud Dashboard > Settings. Wait a few minutes, then re-enable it. Then see if the issue persists.
Generally one can accept the security certificate and gain access to the My Cloud when using the MyCloud.com web portal. the method for accepting the certificate may vary between web browsers. Here is how I did so using FireFox that was posted to another discussion a few months ago .
