The local server (lemmy.nz) only knows about a community if someone on this server has subscribed to it. It looks like no one has. There's also some clunky behaviour that if you search for a community that the server doesn't know about, it shows you nothing, but if you wait a few seconds and search again it will find it.
I just subscribed to that community so it's working now. You might not initially see all comments though.
Thanks, Now it works I can search and subscribe it from Jerboa
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So how can I subscribe to the community if no one has subscribed?
I think of it in terms of - a search can either do discovery of unknown communities, or a look through known communities, but not both. So you do one search to discover and then a second one to approach.