We're currently investigating how to enable instant syncing in these situations.
When accepting a shared calendar, you might see an HTTP 500 error. If you see the error more than once, contact Support.
If you have multiple Apple IDs that you use with i Cloud, you might be logged in to i Cloud for Windows with a different account than you are on your other devices.
The shorter the refresh rate, the more up-to-date your calendar will be.
The longer the refresh rate, the less up-to-date your calendar will be.
Use this page if events you created or updated aren't showing on your computer or in the Google Calendar app.
Follow these steps on the device you're using the Google Calendar app on. Make sure you're connected to the Internet Try the steps above first.
The person who sent you the invitation will need to remove your permissions and then send a new invitation.