Cannot contact web site 'https://tenant-admin.sharepoint.com/' or the web site does not support SharePoint Online credentials. The response status code is 'Unauthorized'.
You may get the above message if the account you are using for the migration is not a Global Administrator and is set as another administrator type not related to SharePoint. Try changing the account role to either a 'Global Administrator' or 'Customized administrator' (SharePoint administrator).
If the above steps do not resolve the error. Download and install 'SharePoint Online Management Shell', if not already installed. When prompted, log in with your Administrator account and run the below command.