When you created your event, you selected whether you wanted Leads to be created for Delegates and when you wanted them to be created (never, on registration, on attendance, on survey completion).
How EventSpark responds and whether your Leads are created depends on two things.
What duplicate rules have been specified in our Salesforce org by your System Administrator.
What you have specified for the Event.
For example, if the duplicate manager in Salesforce is on and your organisation does not allow duplicates to be created, EventSpark will not be able to create those Leads regardless of what your event settings are, and the Leads sync process will fail.
In this case the Leads Status field will be set to Failed by EventSpark on the corresponding Delegate record after the Leads Sync Batch Job runs and the Leads Status field will be set to Duplicate.
If you select Create/Update Leads then the alert will be ignored and the Leads will be created, whereas if you select Do not Create/Update Leads, we will honor the alert and no Leads will be created.