Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for best assistance and troubleshooting: https://support-en.wd.com/app/ask
Has any of you found a solution to this? What filesystems are in use? I noticed from the screenshot posted by Nick that Disk Management doesn’t report what filesystems are used on the 4657.53 GB disk (disk 2). This typically means that it’s an unsupported filesystem, probably something that you can use on a Linux system but not on a Windows system, something like Ext4 or maybe Btrfs.
Perhaps it’s for this reason that WD Drive Utilities can’t find the drives? I can’t recall I have ever used WD Drive Utilities before, so I’m not sure what it can do or what filesystems it supports. But there are several filesystem drivers you can try that add Ext2, Ext3 and Ext4 support for example to Windows systems. There is the classic Ext2Fsd by Matt Wu. There is also Ext2 Volume Manager by the same programmer.
I’m not sure about the status of these applications, and whether or not they are still in active development. But there are also file system readers and inspectors, as well as third party disk management applications that have support for these non-Windows filesystems, that you can use in Windows, to read from, write to and clone disks and volumes or partitions that use these filesystems. For unsupported filesystems, you can sometimes clone these disks as raw. I believe you can use MiniTool Partition Wizard for this as well. Have a look at this 2 year old Reddit post for more options: How to use ext4 filesystems in Windows. I hope this helps.