After having an issue reinstalling CCleaner. I uninstalled it. When I try to reinstall I get the subject error, Error code: 0x80070043, network name cannot be found. Windows suggest I run network diagnostics, which couldn't identify the problem.
That's a network error saying that a server cannot be contacted for whatever reason.
The server could be down, your AV/firewall may be blocking access, something else between you and that particular server (eg. your internet service provider) may be having a problem.
The latest CCleaner is v5.83.9050.
I suggest that you download the 'Slim' installer from here (3rd one down) and use that to install the latest CCleaner:
https://www.piriform.com/ccleaner/builds
(That 'Slim' installer installs exactly the same CCleaner but it doesn't try to contact the same servers during the installation).