The correo argentino page has different search pages depending on the kind of shipment. If you have the tracking code, you have to look in the specific page for your kind of shipment. There are drop-down menus so you can’t get it wrong.
And there are drop-downs also in the search result. It is not very intuitive.
You can also try to call over the phone their customer service and inquire.
I always use the link below. However this week it always returns no results. Even when leaving a zero out to make 8 numbers.