Originally Posted by
Northern Canuck
"You’ll be offered the Air Canada Stopover option when you purchase a one-way or round-trip ticket (any fare) at aircanada.com or through your travel agent
You said you booked through Aeroplan, which is not aircanada.com or your travel agent.
If you have been successful at getting this before, then I think you have been lucky as the intent of this programme as I understand it is not for US-Canada itineraries.