This is not about your app. Looking at the community from your instance, you'll notice that all posts before Marcillepost 13 have only one upvote, and no comments.
This is because the community only became federated to lemmy.ca when someone on that instance subsribed for the first time, triggering lemmy.ca to fetch this community from ani.social. This process syncs all posts, but not past votes or comments. Only from that point on, after that first subscriber, does everything make it over to lemmy.ca.
You can force a sync of a certain comment, if you grab its share URL from ani.social, and pop that into search on lemmy.ca.
