I have an Air Canada (Aeroplan) booking. The first flight is departing tomorrow from Podgorica on Austrian Airlines. When I attempt to check-in through the Austrian site/app, I get this error:

Error
APIS document error: Invalid document number for nationality CAN.

Has anyone run into this one before? Any idea what I can do, short of waiting until I get to the airport tomorrow? I double-checked and all of my information is correct (including passport number).