This morning I received the check-in now email so when to the app to check-in. No go. The flight shows in my "Trips" and in "Flight Status" but no option available to Check-in. So I tried "More ..." and Check-in button, copied in my PNR for the upcoming flight. Still no go, error message indicates they were embarrassed. I would be too.
Used my desktop and the aircanada.com website to check-in without issue and send my boarding pass via SMS to my phone.