What does your booking look like on aircanada.com?
They send e-mails even if only one leg has been cancelled. But if indeed there remain flights operating, they'll need to rebook. If there is not any, they only offer credit, no matter how objectionable that is, read the other thread.
But you'll need to deal with Expedia... Which is one good reason never to deal with them and similar sites and whenever possible to book directly with an airline. Or with a competeent real TA, and pay whatever (small) fee.