Originally Posted by etgohomeok

I have the same issue with one of my Aeroplan bookings (but my other one is working fine). Does yours have any flights operated by third-party carriers by any chance? My suspicion is that the seat selection on my booking is failing because one segment is operated by ANA. The other three are Air Canada metal and i can access the seat selection screen for them but get the same error message as you when I try to confirm the selections.