The error is coming from Kusto service not being able to download the blob, either the Kusto managed identity does not have permissions on the storage account or the storage account is not part of the private network (sounds like this is the issue given the answer @hello provided)

How does LightIngest works:

1. The tool first lists the blobs in the container given the permissions either in the -source cmd arg or some other cmd arg (i.e. here connectToStorageWithUserAuth), here its using user prompt authentication, so given the user running the tool has permissions to list the container the tool will be able to list the blobs.
2. The tool issue queued ingest (given you are using the suggested "ingest-" service URL), with the constructed URL based on the -source and other cmd args, (i.e. here - ingestWithManagedIdentity), here the resulted blob urls are of structure: "https://storage.blob.core.windows.net/container/blob.csv.gz;managed_identity=system"
3. The tools poll the ingestion result (unless disabled).

See LightIngest managed identity docs and the code