And I have an official version of Windows 10, official French localisation, running version 1607 (build 14393.693.)
Unistalling completely and reinstalling this update does not work: your version check refuses the installation.
Installing the revious version CCleaner 5.25 instead of 5.26 works without problem.
The problem is in your installer which does not even attempt to installa anything and rejects my system version without copying anything (and without even creating any debugging log anywhere: nothing in CCleaner install folder, nothing in %TEMP%, nothing in Windows\Temp, nothing in Windows event viewer.
My opinion is that the installer attempts to use an incompatible/unsupported Windows API to make its system version check, and fails to link to it, or passes some invalid parameter (e.g. wrong buffer size for results, or assumption about this size: it was probably compield with an incorrect version of the SDK, or not fully rebuilt from sources and now the installer mixes some .obj/.lib files compiled from another SDK version and some others with a new SDK update where some system structures are now extended).
Note that this is concommitent with the recent Windows update and the apparition of a new SDK! You have probably compiled your installer with this new SDK (for test only, for for use in releases).
Please rebuild your installer with some "make clean". I'm sure it is incorrectly compiled: using a DDK investigation tool, I clearly see that the installer makes false assumptions about system structure sizes needed and it gets an error because your allocated structure is too small to match the version you want to check !