The element may be identical in your source and destination environments.
When Salto compares environments, it doesn't show elements which are identical across the environments.

Your environments may not have been recently fetched, which means that Salto may not be aware of some recent configuration changes. Fetch your source or destination environments for Salto to get the latest changes.

Your adapter isn't configured to fetch the element type you're looking for. Check your adapter-specific documentation to understand how to include additional types when fetching applications.