When trying to download the manifest package generated after using the Insane Mode, Sharegate displays the following error:
Unable to download the Manifest package: it may have been deleted from your Microsoft Azure storage account.
The manifest package contains the metadata that Office 365 will use in order to import the list items and documents. It also contains log files generated by the import job. Those files are located in the Azure Storage account provided in.
This error can happen when the files are no longer present in Azure, most likely because the files were deleted or if the storage account was cleared.