I have a problem, that my Canon printer doesn’t print duplex, when I select “2 Seiten auf ein Blatt” and “Beide Seiten automatisch” with a range of not following pages or flows (on DIN A 3).
Printing the whole document with these settings works as expected. I’m on Win 11.
I’ve just tried this out here with my own printer and it works as expected. Are you trying to print a booklet or 2-up/spreads, or regular individual pages?