Hello spike589715, welcome to the Community. Have you tried to ping the My Cloud to verify if it’s still recognized on the network? If it is, try to map it again using the network name or the IP address.
The full safepoint backup always seems to take forever and probably makes the MYCloud unresponsive so I usually do this when I know that I will not need access for 24 hrs, however when you update the safepoint, only differences are saved so this is usually very quick.
Be warned you may not be able to restore from the safepoint using the dashboard so not as functional as it should be but as the files are stored as full files within their shares it is easy to restore manually after reconfiguring the MYCloud