Cross site publishing depends on the search to create a content source and to manage crawling for SharePoint cross-site publishing. In SharePoint, content source will specify crawling in SharePoint farm. By default, after creating the search service application content source will be created in SharePoint farm.
We can re index content source that contains the catalog for changes to be added to the search index. We can re index the catalog content by using the steps below,
Navigate the library/list and go to settings page. Click on Advanced settings in General settings section.
Click on Reindex List link in Advanced Settings Page Reindex List section. And click on Reindex List to confirm to the catalog to be reindexed during the next crawl, click on Ok.