Import update with barcode as identifier

It makes sense to allow barcodes to be identifiers in import as it is the only thing that is the same for everyone. To work around this I have used barcode as item_code. But still, somehow it can’t find items even this way.

I mean in the database item_code is let’s say 4560842037320 and in the update file, item_code is also 4560842037320. How is it possible that the item is not found then?