Was it on the AC app? Were you all picking seats as opposed to one selecting a seat and one looking at the seat map from flight status?
The latter will show blocked seats as occupied, but they may be available for seat selection. Could it be what happened?
Two individuals, both using the web checkin. The map was very different, for one passenger it only showed almost all middle seats as available, but no other seats. For the other it showed a more random map, with some middle seats, a few aisle seats and very few window seats available.
