Tried to install 5.22.5724 from 5.17.5990 and I get the message "0x2efd: A connection with the server could not be established." I have tried entering my license (which appears on the 'about ' page) with no change.I have gotten this message for over a week . Thanks.
Have you tried downloading from here to your downloads and then installing?
https://www.piriform.com/ccleaner/builds
Or try uninstalling your present version and installing the new one (make a note of your license first.)
Let us know how it goes.