Win 10 - Inaccesible boot device error with Blue SN500

I have two Maximus IX Hero mobos that were configured with the same hardware: I7-7700K cpu, BIOS 1301, 32GB (2x16GB) DDR4-3000 RAM and Seagate HDDs. They both booted and ran fine with HDDs. Recently I got a good price on the new Intel SSDPEKNW020T8 NVMe PCI-e SSD. I plugged it in, used Casper 10 to make a bootable clone, told BIOS to boot from the new drive and wa la – worked perfectly and runs like a bandit. I notice that Intel provided a driver for it.

A couple weeks later Amazon had some really good pricing on the new WD Blue SN500 NVMe SSD (WD-WDS500G1B0B-500GB) and I bought one. Using the first PC’s “twin” I then went through the same installation steps. While each step completes without error I have not been able to boot from it. It did not install its own driver, just the Microsoft Standard NVMe driver.

I can access it fine. Casper makes what appears to be a perfect clone and I can easily move files to/from it. It just won’t function as a boot device. I get the blue screen abend with the “inaccessible boot device” error.

It looks to me like the BIOS for each machine is configured the same. Just to make sure though I loaded the exact same BIOS parameter values from a USB into both machines. It made no difference.

The Dashboard shows everything to be healthy, working fine and up-to-date.

Does anyone know why this drive seems to work in every respect except as a Win boot device?