Unfortunately, some folks have encountered significant issues with Windows 10 version 1903 and monitor ICC profiles (seems to affect 10 bit panels in particular, such as those from Eizo and BenQ).
The results we're seeing are resulting in failing validations after calibrations. It seems as if the calibration adjustments are not actually being applied.
This issue is affecting a multitude of systems - Eizo have a support note for example (although they are now stating it is solved by the latest update, see below). It also affects BenQ hardware calibration monitors, as well as other monitors using simple software calibration.
In short, any monitor calibration scenario may be affected.
The first thing to do is check which Windows version you have. Microsoft have a simple guide for this.
Not yet running Version 1903?
If you're not yet running version 1903, simply hold off updating for a while until the problem is confirmed solved in all cases.
Already running Version 1903?
An update had just been released that seems to solve the issues....most of the time! Go to your Control Panel -> Updates and click 'Check For Updates' - you should see a new update called 'Cumulative Update for Windows 1903' is available. Download and install this update.
After installing this specific update (KB4505903), also update your graphics card drivers to the very latest version (visiting NVIDIA/AMD/Intel directly is usually the best way to do this).
Reboot, then re-run any/all monitor calibrations.
This has solved the issue in most cases we've seen so far - but unfortunately not all of them. One expects further fixes will arrive from Microsoft (or possibly BenQ and Eizo although it's an underlying OS issue, so really MS should be the ones to fix it really!).
Folks are reporting that if they change the gamut in their calibration target, this can solve the issue. So if you're using Panel Native for the gamut, try setting that to AdobeRGB instead (and vcie versa). Panel Native and AdobeRGB are effectively the same thing with most modern wide gamut monitors, so really using either of those is an acceptable work-around for the issue.