Modified By and Created By users are not preserved, how can I fix this?

There can be a number of reasons why some users in your Modified By and Created By fields are not preserved. Verify the following scenarios to determine how you can handle the missing users:

• The users do not exist in your destination. The ShareGate migration tool cannot preserve your users in the Created By and Modified By fields during a migration if the associated users do not exist in the destination. You can find more information here.
• You do not have sufficient administrative access or certain permissions on the destination to preserve those users.
• You might need the server extension to preserve your users.
• The copy option Preserve authors and timestamps is unchecked.
• Office is not installed on the machine running the ShareGate migration tool. If you are copying local files to SharePoint, the ShareGate migration tool extracts properties from Office files.
• There is a Workflow or Event Listener on the list modifying the Modified By when adding or updating an item. You must disable it and restart the migration to keep your users.