If an event had failed for some reason, SQL, Email, Actions, or Reports... KS would continue to try and if the problem resolved it self then it would complete successfully. In version 10 a limit of retries has been instated. Please allow "Unlimited Retries" as a possible selection for the event.
This is critical when the issue is out of our control such as meeting a SMTP quota. They need to keep trying until the quote resets.
In other cases sometimes the files that the event is waiting on is still being generated and is not available right away. KS should continue to retry until the files are available.