Start with the website of the postal system of the country you bought from.
At least you should see the date the parcel was accepted.
Many sellers don't use full "tracking" which is quite expensive. They only use Delivery Confirmation which is all that PP demands in Disputes over delivery.
If the parcel has arrived in Canada, go to canadapost.ca and look for the number there. Again, if the seller only used DC, there will not be any notes.
What is the real problem?
You have up to 45 days to start a refund claim for "Item Not Recieved".
Allow 20 days for arrival from North America.
Allow 15 -20 days for arrival from Europe.
Allow 30 days for arrival from Asia.
If you have not recieved the item, first contact the seller. If he does not respond or if the response is unsatisfactory, start an Item Not Recieved claim. (Look up in the top right corner of this page, under Customer Support)
If the seller cannot prove delivery, he must refund or get a black mark on his seller account. If he does not refund, PP will and go after him for the money.
Do NOT accept an offer of replacement. Ask for a refund. If you still trust the seller, you can then re-order and start the transaction from Day One.