Does the seller have a shipping price for Canada? It sounds stupid, but never overestimate intelligence.
Does the seller have other items for sale? Have you tried asking a question through any of those?
Have you ever received a Strike for an Unpaid Item? Most sellers have a Block against bidders with Unpaid Item Strikes.
Do you have an active Paypal account? Many sellers will not accept bids from bidders without active PP accounts.
Have you ever bid with the seller before? You may be on his Blocked Bidder List for some other reason.