We do not currently support the migration of the following:
Audit fields import for Attachments. (if you think that this feature is important for your Salesforce CRM, you can vote for implementing it here)
Ownership for inactive users. Your user must be active in order to be assigned as owner for an imported record. You can read more about that here.
Please note, you must have audit fields enabled for us to import converted leads. If you do not have this feature enabled, we are unable to import the converted leads, because Salesforce does not allow us to denote the lead as converted
In addition, Opportunity Contact Roles are not imported by default. If you need these imported, please send us a message and let us know so we can enable this for your migration.