Did they specify they refused or it is an intention of refusal??
Did you apply online? If so, you can view the refusal or the intention to refuse letter in your account. They don't send a letter by mail after refusal to my knowledge (well I don't get refusals...).
If you applied paper, ask them to send you the refusal letter again.
Do you know why you got refused? Was it your first CAQ or a renewal after you studied here?
If itvis a renewal, describe what you did in Quebec after you got your first CAQ.
I don't think it was your first CAQ application from outside of Canada. It's pretty hard to get refused in these cases since you only need to provide an admission letter, photo, copy of password and signed form.