Sending, receiving, and organizing email in Outlook.com
+1 Same issue. Worked until a few days before, but no longer. Both not in Outlook for Web and "New Outlook".
See also last answers in this thread: https://answers.microsoft.com/en-us/outlook_com/forum/all/synchronizing-new-outlook-with-google-calendar/cfc19099-5dca-4c93-82fc-c465b9b1e5ce?page=1
Check out the thread. It helps to understand the issue.
Got the calendar working by using the new Outlook desktop app (added my Google account to the Outlook app). Didn't work with the old Outlook desktop version.
I was using the web app over the desktop app only because of aesthetics. The new desktop app looks exactly the same as the web app so I'm willing to make the switch. Sadly, it's not a solution to many of you, but maybe alleviates the problem for some of you (until a fix is found).