It may be an automatically opened Unpaid Item Dispute. Many larger sellers use those since they generally can be handled by robots.
There is a place to put your Response.
Politely remind the seller that she doesn't ship to Canada and did not give a shipping price to Canada. Then still politely ask that the UID be closed.
She should have cancelled as "problem with address" or even "buyer request" either of which will end a transaction with not fallout for either buyer or seller.
Worst case is that you don't pay and get a Strike which will stay on your record for 12 months.
If you buy rarely, this will not be a problem. Strikes are kept private.
However, a second Strike during 2021 would automatically Block you from buying with many, perhaps most, sellers.
It is useful to read the Shipping tab on any listing, since Free Shipping is normally only Free Domestic Shipping. The cost of international shipping is much higher, never mind tracked international shipping.