When you create a container from within the program code, it is by-default set to private. This is when you will not be able to access it directly. You need to set permissions explicitly on the container.

Setting permissions explicitly will fix this.

await HttpHandler.tempContainer.CreateIfNotExistsAsync();

BlobContainerPermissions permissions = new BlobContainerPermissions();
permissions.PublicAccess = BlobContainerPublicAccessType.Blob;
await HttpHandler.tempContainer.SetPermissionsAsync(permissions);

blob = HttpHandler.tempContainer.GetBlockBlobReference(blobFileName);
await blob.DeleteIfExistsAsync();
await blob.UploadFromFileAsync(file);