Sorry your package appears to have gone AWOL. But keep in mind that DHL is a shipping company. A human being left your item in your apartment building's lobby, not a company. It may be that because they're not accustomed to making residential deliveries, the human being had to make a human judgment call and made a human error.
I suspect that the Global Shipping Center is using more alternatives to the freight-Canada Post combo because of a backlog at the Canada Post Gateway Facility in Mississauga. There have been a few posts recently expressing concern about GSP-forwarded items with tracking dead-ending in Kentucky or at customs and I suspect those items are waiting to be processed in Mississauga.
How do you know your item made it to your apartment lobby if it's not there, though?