You need to at least search for remote communities from your instance to see their content appear. Keep in mind it's not retroactive though (I think), you'll see content from the moment you made the search.
Lemmy Support
Support / questions about Lemmy.
Alright, so no way to manually trigger a sync to get missed stuff?
I don't think so but maybe you should get confirmation from the Devs. I don't know if you're in the same case than me but I made a script to workaround this federation issue. Maybe it could be useful to you. I explained it in a little blog post
If some user or your instance subscribe to one of these communties, sync will be made as far as this user is there.
That's really weird, the instance seems to not sync some posts and no errors from here.
Asked the admins of the other instance if they had any on their side.
Are these posts made by people from the instance the community is set, or by external people also subscribed to the community?
Usually from people from the instance of the community itself.
Maybe better to make a report in Lemmy repositories.