Received the AC email last night to invite me to do my OLCI for my flight to CDG tonight on AC8723, then on to AC870. Clicked on the link and got the response that one of the flight was not open yet and to check later. Went to bed and tried again this morning, got the same message, more than once and the flight is in about 12 hours.

I know that 870 is oversold, could that explain why they're not opening up the flight?