Calendar app is not opening

Desktop

Verify that your browser is not blocking pop-ups. Look at the top right of your browser bar for an alert that says "Pop-up blocked". If you see this alert, click on it and select the option to allow pop-ups and redirects.

Once you've allowed pop-ups, you'll need to refresh the page and subscribe again.

Still not working?

You'll need to manually import the calendar or switch to Google Connect for calendars to be added in the background, across all your devices.