Run Button is disabled during the post migration step. It is showing as Read Only
Archive set is migrated successfully, but the Run Button is disabled ( greyed out ) during the post migration step. It is showing as Read Only.
This is causing only for this CSR, for other CSR's the Run Button is enabled.
Migation was completed with errors
The reason the run button is disabled because the migration completed with errors. Take a look at the migration history to see which object failed to migrate and make sure to fix that object so that migration can be completed successfully.