Events that are associated and attached to the "Close" Activity Notification, are not firing.
Steps to Reproduce (Example)
1. Create an event with a 10 secs delay
2. attach this event to the "Close" Activity
3. open any Incident and change the status to "Closed"
You may see (in the Event History) that the event was attached to the Incident and immediately cancelled
This is by Design. Whenever a ticket is set to closed, all events that are associated to the ticket are shut down and will not fire.
In some releases of SD, it was found that some events were being allowed to pass despite the closed ticket status. Such an issue is addressed in release 12.7 CP2 and 12.9. For earlier releases, the concern and corrective actions are described in Problem USRD 1937 for CA Service Desk Manager.