Aeroplan has been unable to book award travel on several Star Alliance airlines since late August. I reached out to them to see what was going on and they assured me that the issue was a technical problem, that they were working on it, and that they wanted to get it fixed quickly.
However Aeroplan seemed confident that wouldn’t be the case here. I wanted to see the proof that this would be fixed quickly, rather than taking them at their word. It turns out that they fixed it quickly (mostly).