Please ensure all the users whose file permissions has to be migrated to the target are available in the “Application Users Mapping” which is placed in the Settings -> Users Mapping tab. Post adding the missing mappings, retry the job.

(OR)

Post the migration is complete, Please open Migrate -> Migration Jobs -> Edit Job Settings for the problematic job. Under section Mapping Not Found Users , map the target users (whose files permissions has to be migrated to the target) and retry the job. This would resolve the “Failed Permission” issue.