Yeah, it's not blank it should have a number below it. Copy and paste it here for order tracking:
http://www.tnt.com/webtracker/tracker.do?navigation=1&respLang=en&respCountry=gb
so, those who can use tnt tracking, on your apple order screen (on the blue header banner where it says date shipped)
does it say its coming via tnt uk or just tnt???
my theory (probably wrong) is that those that can track isnt coming from tnt uk! hence the fact you can track as your parcel is in motion