Google and Apple calendars are not playing friendly right now.
As alerted to us by multiple MacRumors readers, there appears to be a syncing issue with Google Calendar and Apple's Calendar that began within the past 24 hours or so. The issue prevents Google Calendar entries from appearing in Apple's Calendar app on the iPhone, iPad, Mac, and other devices.
The underlying cause is unknown at this time, but anecdotal customer reports across the Google support forums and Twitter suggest that the issue is on Google's end. In any case, a fix is likely in the works.
Article Link: PSA: Google Calendar Experiencing Syncing Issues With Apple Calendar