It's probably with Canada Post and will arrive by Wednesday.
If you are not home , a Delivery Notice will be left telling you where and when it can be picked up.
Usually this is the local Postal Outlet.
If more than 20 days have passed since payment, go to the Resolution Centre at the bottom of this page and open an Item Not Received dispute.
Mention that this is a GSP transaction.
If the GSP cannot prove delivery, you will be refunded in full.
If the package shows up after that, the GSP doesn't want it back, and the seller has the money and is not entitled to it back.
So now you have a real problem.