CCleaner says Outlook 365 is open

When I try to run CCleaner it says that it must first close Outlook. When I say OK it says it is not closing, do I wang to force it to close. I say yes and it proceeds. Problem is that Outlook is already closed and was not shown in Task Manager as being open. Any idea where this ghost Outlook is running and why?

I have exactly the same problem but with Google Chrome browser. I do use Outlook but that doesn't give me a problem. Will be interested in any replies you get. I had started to think that Google Chrome does not close when you think you have physically closed it and continues to monitor your every click! and even your conversations as often notifications appear when you have been talking about a particular thing. I have become extremely paranoid!!