Make sure that your event has been published and is not still in draft status. 

To publish an event, follow these steps:
  1. Open the event editing pages.
  2. Click 9. Publish. The Publish settings display.
  3. Select Published (Public) or Published (Private) under Event Status.
  4. Click Finish or Save.
  5. To direct people to the event page (especially if this is a private event), copy and paste the Event URL.
If the event is published and you still see this page, check the security category of the event to make sure that it is set appropriately.