Yes.
You have to go to the app for turkish, and have the turkish booking reference, which you have. I don’t think the website works for it with aeroplan bookings.m
And even then, the app can send you round in circles because it seems to update at a different time to the main system.
For example when they changed my aircraft from an a330->a350, the booking itself and seat selection tool was blocked for like three days until the app updated with the new flights.
Hiwever, you can also email the TK office in australia… they responded overnight last time.You can do a dummy paid booking on the TK website, pull up the seat map, see what’s free, the. send an email to TK with your seat selection.
But the app is easier… when it works!