@Fgbd009 There could be different reasons for this. One is that federation with the home instance might be broken or slow.
Another reason has to do with the way the activitypub protocol that the Fediverse is designed around, basically assumes you're only interested in new content when you subscribe to a magazine/community.
For what it's worth, I've discussed why this causes problems for new users in more detail here:
https://kbin.social/m/fediverse/t/131225/Making-threadiverse-communities-more-discoverable-some-suggestions