Maybe they haven’t federated yet? No instances afaik autopopulate a community with all the posts the community has as that would easily clog all instances involved. Relays could help but they’re rarely a reality in ActivityPub.

If that’s the case, an option you have is to get the link to these posts and search for them in your instance’s search field, so you can import them.

I can see posts from both.

I cant see posts from at least one individual though. Bug might be related?