The CCleaner Cloud agent has 2 components, the tray application and the service - both need to be running for CCleaner Cloud to work properly.
If you are experiencing a technical issue with CCleaner Cloud, the first place to start is to check that both these components are running properly.
Checking the service
Open the Windows Task Manager (ctrl > shift > esc) and look for CCleaner Cloud Service.
If the service is not Running, then right click it and select Start Service.
Checking the tray application
You should see the CCleaner Cloud icon in tray.
If not, then you can start the application from the Start menu.