Because Meta doesn't accept every conversion event for every objective. Create campaign and Duplicate with Change objective/destination only show events in the Conversion event field that work for the chosen objective.

  • Sales: Lead, Contact, Submit Application, Schedule, and Find Location are not available. To optimize for them, create the campaign with the Leads objective.
  • Leads: Purchase, Add to Cart, Initiate Checkout, Add Payment Info, Add to Wishlist, and Donate are not available. To optimize for them, use the Sales objective.
  • Both objectives support: Complete Registration, Subscribe, Start Trial, View Content, Search, and custom pixel events.

In Create campaign, when the field is empty, the caption below it lists which events are unavailable and which objective they work with. If an incompatible event comes from a draft, the field resets to empty. Ads Editor also blocks creation before touching the account and tells you what to change.

Without this rule, Meta would reject the ad set ("Conversion event unavailable"), and sometimes an empty campaign would be left behind in the account.