As far as I understand, to see the posts you need at least someone from your instance to subscribe to a given community, and only after that you'll see new posts going forward (fediverse pushes content to other instances instead of pulling all the content on request). And you won't see any pre-subscription posts anyway, since it's apparently a lot like actual irl magazine subscriptions — you only get the new stuff once you subscribe.
So, subscribe and wait for a day or two, and you should see new posts appear in your feed.
shepherd
TelKaivokalma