I submitted a couple of APPR claims back in late June/early July and haven't yet received a response back from AC (despite them promising to get back within 30 days). The first one was a delay of over 9 hours due to the flight I was originally booked to be on being cancelled due to crew scheduling issues which so far as I can tell is completely within the airline's control. On a whim, I thought I'd call AC reservations to see how on earth I should follow up with this and was given a hint which I think maybe be helpful to those on the forum: if you click Customer Support on the Air Canada website and click the red chat button on the lower right, you can simply paste your case number in and it will tell you the current status. Not as good as getting a prompt response but at least we know what the status is and have a way of tracking the lead time on responses since we can screenshot the response.
-RooFlyer88