As of 9-13-16, the CCleaner setting "Skip user account control warning" is not working with Windows 10. When trying to check the advanced option "Skip user account control warning" I get the message "system cannot find the file specified". This originally happened with CCleaner version 5.22.5724 (64 bit). I uninstalled that version, and I reinstalled version 5.21 to see if that would work with the "Skip" advanced option. Unfortunately, version 5.21 also yielded the "system cannot find the file specified" message.
It appears that perhaps Windows 10 moved or removed the file needed to activate the "Skip user account control warning".
Perhaps you can find another reason that the CCleaner setting "Skip user account control warning" is not working with Windows 10.