Calendar would not synchronize after installing and running the newest free version of CCleaner. I cannot 100% blame CCleaner for causing this glitch, but when I uninstalled CCleaner and tried synchronizing the calender with Outlook.com, still nothing happened. My next choice was to use my eM Client Backup and Restore. That didn’t help either.
I decided to delete my outlook.com email account from eM Client, close eM Client, launch it again and add my Outlook.com email account again. Voila! Now my calendar is synchronizing with the web account and my Mobile Phone calendar.
Like I said. Could it have been CCleaner that dug to deeply into an (app data) file and corrupted my account information? I don’t know, but I do know the process I explained above got me back to where I’ve been for over a year. A happy eM Client user.
Finally, I would like to say that since Avast acquired CCleaner I will never used it again. Not just because it “may” have caused the sync glitch but because of the free version Nag Pop Up.