Run Ccleaner's registry cleaner. Select the 'fix' tab and don't save. Reboot, which is important. Try installing the latest version again. If that fails then use the removal tool. Download and save to desktop. Reboot to safe mode and run the removal tool. Re-boot and try to install the latest version.
How to get Windows 10 now: how to download and install Windows 10 even if GWX.exe is missing