So I am flying Flex to BRU tomorrow and put my name in to upgrade to Premium Economy upon booking. I have an initial connection (YOW-YUL), and checked in for that. For the YUL-BRU, the web/mobile check-in showed "Check-in not open for this flight" both at that point and even once it was less than 24 hrs before the second flight.
I was able to check in separately on the mobile app by using YUL as my departure airport instead of YOW, and I'm still on the upgrade list (although PE is full so I assume my chances are slim)...was this a temporary bug, or is that how waitlists work?