After trying for more than a week, I was able to reach an Aeroplan agent. Indeed the itinerary was no longer in ticketed status, because the schedule change had turned a non stop into a connecting flight and that connecting flight would have had ordinarily incurred a small extra $ cost (same mileage cost). The agent initially tried to push through to ticketed status but it didn’t work, so she had to get in touch with ticketing and notify them that it was an involuntary change. Everything worked after that and I checked on cowtool to ensure all segments have HK status and have fare basis assigned.