Community content on another instance not populating?

So I just downloaded Liftoff and found a couple of communities on an instance I'd never heard of before, and I decided that I wanted to subscribe to them on my lemmy.ml profile. We are federated, and when I view the communities through the main instance I see a bunch of posts and subscribers, but when I try to view them through lemmy.ml it says there is 1 subscriber (me) and no posts. I tested this on my mobile browser. Jerboa, and Liftoff all with the same result.

Is this one of those cases where it's a bug and will sort itself out, or am I doing something wrong? I don't wanna miss out potentially cool communities if they just aren't coming up for me