I've booked a lufthansa flight via an online agent, and one of the legs (MUC-YYZ) is operated by Air Canada.

The seat selection at lufthansa.com doesn't let me choose a seat for this leg, and I can't access the booking at aircanada.com either.

Naively, I figured that the "efficient and seamless travel experience for customers traveling on different star carriers across the star network" slogan had anything to do with reality. Obviously, I was wrong, but is there any other way I could select a seat for that flight? I've purchased a quite pricey J class ticket and selecting the right seat can make or break the whole experience.

Thank a lot for any help.