This can happen if the event in RE is inactive or doesn't have a start date or end date specified. To check these fields, login to The Raiser's Edge, and open the Event.
  1. Go to Records> Events and search for desired event
  2. On the General tab, confirm the Start date and End date fields
  3. Confirm the 'Event is inactive' checkbox is not selected
If you are not able to see any events from RE in the cross reference, then this could potentially indicate a connectivity issue with your server or web services. Verify the connectivity to Wed Service to sync data between Luminate and RE.