The USPS does not have tracking. Their service is called delivery confirmation and is for that in a nut shell. Unlike other services that have live updates from the route all along the way the postal service scans during the day and updates on return to the office. Also in hubs, which is where your package is more than likely last scanned at they do not always, more like ever, scan on leaving the hub. Meaning your package may be on truck to your area's main hub and still showing at the vendor's hub.
Where ever you go,
There you are.