If you previously mapped the My Cloud to your Mac it is possible the IP address changed which is what the error message appears to indicate. You may have to disconnect/remove the existing My Cloud mapping from the Mac Finder and create a new mapped link.
What is confusing about the My Cloud Dashboard? Can you post a screen shot?
The My Cloud Dashboard is not a file manager. The Dashboard is for configuring the features/options of the My Cloud.
If you didn’t change the default My Cloud name it should be:
If you want to access the My Cloud by it’s IP address you can access your local network router’s administration page and see what IP address the router has handed out to the My Cloud. See your router’s documentation for more information on how to access it’s administration page.
That warning is just a standard warning message. Any time one does anything to the firmware there is always a slight risk of possibly corrupting the firmware. Like any hard drive the My Cloud’s internal hard drive can fail which is why WD included the capability to backup the My Cloud (using Safepoint or Backup in the Dashboard) to a USB hard drive attached to the My Cloud’s USB port.
You may also want to try a 40 second reset using the reset button on the back of the My Cloud if you haven’t already and see if that clears the issues.
Yes. One can remove the hard drive from the My Cloud enclosure in a pinch. Its how one can “unbrick” the My Cloud. If one has Windows they will need a third party driver to read the Linux partitions on the My Cloud drive.