After booting my PC, the CCleaner icon appears in the system tray / information area, ''blinks' (checking for updates?) for a couple of seconds, and then disappears.
I've only noticed this to since updating to Windows 10 v 21H1 RP (Build 19043.985) x64.
I'm running CCleaner Professional v 5.79.8704 x64.
What you are seeing is "Launch the CCleaner app window each time the computer starts" from Options>Settings, which your screenshot shows you have ticked.
(Despite what it says it doesn't open a window, it could be worded better/simpler to say what it actually does).
What it does is run a clean each time you start your computer, the flashing icon in the System Tray shows that it is cleaning and then it goes away when it's finished cleaning.
There are two CCleaner settings that will make a CCleaner process run in the background and so either one will leave an icon in the System Tray all the time:
Keep CCleaner Updated Automatically.
Smart Cleaning (any of the Smart Cleaning options).
If you don't want either of those running and just want a CCleaner icon that you can launch CCleaner from quickly then you can 'Pin to Taskbar'
If you could tell us what it is that you actually want to do then we can walk you through how to do it.