Backup problems on MyCloudEX2Ultra

I have a network connected MyCloudEX2Ultra that I use for backups using Time Machine. This has worked well for over a year.

Recently (perhaps after updating OS to Catalina), Time Machine says it must perform a new backup (which involves deleting all old ones). It completes the backup, and then wants to perform a second one as verification. This -always- fails, and the process starts over again making a new backup. This has been going on for weeks, and so I now have no reliable backup.

I've read on a forum that Time Machine under Catalina is notorious for this problem, so I have downloaded a trial of Carbon Copy Cloner to see if that works any better. CCC says that the MyCloud drive is not formatted for Mac, and suggests I use Disk Utility to reformat it. But the MyCloud drive does not appear in Disk Utility (under "Volumes" or "Devices.")

I am stymied. There is an option in the MyCloud Dashboard to reformat the drive, but there are no options in the process. I have done this recently, and yet the drive still does not show up in Disk Utility, and CCC still says the drive needs to be formatted for a Mac.

Any suggestions would be appreciated!