When you click Start Migration Account Objects Preview might warn you that you have invalid objects that have to be corrected; for this, there is the button called Repair Invalid and Proceed.

When you click Repair Invalid and Proceed you will be presented with a choice: Repair Invalid and Exclude Invalid.

If you select Exclude Invalid all invalid values will be skipped, i.e. removed from the process. These invalid values might be wrong email addresses, for instance, the ones that contain special signs not allowed for email addresses.
If you select Repair Invalid you will be able to edit invalid objects manually or use our automatic action for all at once. To see what is this automatic action, click Details.

When our Onboarding tool finds only valid objects that can be created in our system it will allow you proceed to the next step.