Someone was being lazy / didn't want to deal with it. If it says "delivered" and isn't at your house, the tracking starts NOW. If they won't start it now, "may I speak with your supervisor?"
Also important to note: you aren't their customer. ABU / the shipper is their customer, and is the only one they are technically responsible and answerable to. You can't file a claim, only the shipper can file a claim. They paid to ship it, they are the party to the "contract" for the delivery, and they are the ones that will end up with the insurance refund if it's lost etc. So if push comes to shove, they can and might choose not to assist you. At which point you need to contact ABU and turn them loose from that end. The sooner the beter.