If double clicking does not install then it is typically a corrupted Creative Cloud installation or a messed file extension association.
Did you completely uninstall Creative Cloud before reinstalling it? If not then doing that would probably fix it.
You can also try right clicking on the CCX file and selecting open with. If you see the option to open with “UnifiedPluginInstallerAgent” then select that and it will install. If that is missing then you will need to uninstall and reinstall Creative Cloud. If that option is still missing then you would need to contact Adobe to fix Creative Cloud.
Double clicking is suppose to launch “UnifiedPluginInstallerAgent”. If it doesn’t then the OS file preferences are messed up. You can try setting that in the OS. However, I have found that doesn’t always work and removing the CC app completely and then reinstalling will typically fix the file associations.
Let me know if this helps. If not then I think you will need to contact Adobe. CCX install issues are on the Creative Cloud side and they would be the ones that could better troubleshoot and fix it.