Are you meaning the System Tray? (on the right where the time/date is).
I haven’t tried launching from there myself, it may be a bug.
Do you not have an Icon on your Desktop that you can double-click to launch it from.
Have you tried launching it from the start menu?
Either select it from the list of apps on the start menu or open the start menu and simply type- CCleaner - a window should open giving you the option to launch it.
If you are still having problems with CCleaner 7 thenyou can always roll back.
For the download link(s) and roll back instructions click this: How to Roll Back from v7 to v6.39