Drives are not showing up as local devices in FTK Imager AND EnCase

I'm trying to image some evidence for work. An admin shipped out a total of three drives to me. Two of the drives, when plugged into the write-blocker on my forensic tower, do not show up as a physical device in FTK Imager or EnCase. I can't even see any reference to them in Disk Management or Device Manager. The third drive, can be seen and was imaged. But a closer look at it shows that there's no MBR or …

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