Ical won't show google calendars

I have my google account synced with my computer in System Preferences and in Ical. I used to get the following message when I opened Ical and every time it synced. But the google calendar did work. However, the message has stopped but now I can't see the google calendar.

"The URLcalendar.google.com/calendar/dav/_______@gmail.com/user/ encountered HTTP error 404. Make sure the URL is correct