Yes, there is a repair:
Uninstall it. CCleaner is a great app to use in Windows, but totally unnecessary for macOS and can actually do more damage than good. Get rid of it.
If OnyX works when you click on it, then you have the correct version.I already have OnyX and have used it for ages but I didn't realise there was a specific version. I have only used the maintenance I didn't realise there was more to it than that. How can I find out if I have the correct version for my macOS the version I have is 3.4.9 iMac (21.5-inch, Late 2015) running High Sierra 10.13.6.
I have just googled OnyX and found I have the correct version also more information about how to use it.I already have OnyX and have used it for ages but I didn't realise there was a specific version. I have only used the maintenance I didn't realise there was more to it than that. How can I find out if I have the correct version for my macOS the version I have is 3.4.9 iMac (21.5-inch, Late 2015) running High Sierra 10.13.6.
I have only ever use the maintenance in Onyx and run in the default settings, which is what chscag advised, so I hope I have not done any lasting damage.These days I have a tendency to advise OP's just download Maintainence (for your OS) from Titanium Software. It performs all of the same tasks as the Maintenance script in Onyx but without the potentially more "dangerous" Utilities, Files and Parameters scripts which we don't advise anyway.
I used to use onyx on my older mac's but have not even downloaded it for my 2015 MacBook Air running Bis Sur. wonder if I should use this maintenance app for that or not. the laptop is a rocket ship and works awesome now.