I received a reply from x-rite which identifies the issue:
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Rory,
In an effort to resolve your support Case, the following comment has been added. Please review this comment, and respond as indicated.
Comment: The Windows 10 operating system has had its share of color management glitches. I would try the following:
1. If you right click on your desktop and select “Display Settings”, you should see the monitor setup with three numbered boxes. Click on “Identify” under the boxes and make a note of which number pops up on which monitor. Make sure that the “Multiple displays” has “Extend these displays” selected.
2. Now go to Control Panel > Color Management. You need to have three displays in the “Device” drop down. If not, there is likely a problem with the graphics card installation. Click on “Identify monitors” button. Do the numbers that pop up on each monitor agree with the numbers that Display Settings gave you in step #1?
3. If the monitor numeric designation in Display Settings and Color Management do not match, there is a Windows OS problem. We’ve seen two possible solutions:
a. The simplest solution and the one I’d try first is to go to Control Panel > Device Manager and open the “Monitors” list. Right-click and choose “Uninstall” for each of the monitors. After all monitor drivers are uninstalled, reboot the computer and the monitor drivers will re-enumerate. This will many times resolve the mismatch in Display Settings and Color Management.
b. The second, more complex solution is to reinstall the most current video card drivers. I see that you’ve already done that.
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The display settings and color management enumerations are different. I tried uninstalling all the monitors in the device manager and rebooting. Unfortunately this did not work. My Win10 is up-to-date. At least now I know what is wrong.