I will repeat that the exchange rate is not under the control of the seller.
But you have 60 days to leave feedback. The most effective feedback is calm and factual.
Just for interest's sake, was the seller cancelling because he didn't have the item anymore (common with dropshippers), because he didn't get the auction result he was dreaming in technicolor about, or because he doesn't ship to Canada? The last would be your error not his.