When a Data 360 (formerly Data Cloud) activation to Marketing Cloud Engagement is executed, an import is triggered in Marketing Cloud to add the activation data to a Marketing Cloud data extension. During the import some records in the activation data may be "Skipped". Review Rows or records are 'Skipped' in a Marketing Cloud Import file for more information about "Skipped" records in Marketing Cloud Engagement imports.
When records are skipped by the import, they count toward the Rejected count that is displayed in the Activation History in Data 360. However, the reason for these skipped/rejected records is not displayed in the Rejected count popup. If all the rejected records were skipped by the import then no warning icon is displayed on the UI for that activation log and you will not see the Rejected count popup.
Some reasons why you may see duplicates are outlined below:
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