A: Sometimes the sync disconnects itself, this could be caused by inactivity or setting changes made in Office or Google.
To reconnect, go to Settings → My profile → Office 365 Calendar or Google Calendar > click Revoke authentication > click Authorize on Office 365 or Authorize on Google and log in with your Office or Google login details > under Imported appointment activity type, choose the appointment type your synced meetings get > Save.
If Google Calendar is connected but appointments are missing from it, see Why can't I see appointments in my Google Calendar?