Finally fixed ... after trying many times I finally completely uninstalled the (old ver) with RevoUninstall, then reinstalled the old version, and bingo the update worked.
I have CCleaner pro v5.39.
It tells me that a new update is available so I click "Update". It then displays the downloading box and when 100% is reached this box disappears and that is that nothing else happens.
It does not update! Why is this so>
Thanks