I just booked a PDX-YVR-YYZ-SEA-PDX itinerary on alaskaair.com with all flights on AS except for the YVR-YYZ flight, which is operated by PD. I fully expect not to be able to select seats on the PD flight but for unfortunately, when I go to assign seats on the AS flights, I only get the following message:

"The seatmap for this flight is currently unavailable. Please check back later for seat assignments. Seats may be available within 24 hours of departure at check-in, or through an Airport Customer Service Agent on the day of departure."

I've also triple checked to make sure I didn't accidentally book a saver fare and it sure doesn't look like I did. I'm booked into Q class for PDX-YVR and in G class for YYZ-SEA-PDX. What am I missing? Is it the presence of a PD flight that makes it so that the whole itinerary cannot have seats selected online?