It can take a little while for your home instance to federate with the remote server and find/cache the community in question. When in doubt, search for the full URL of the community, that's what works the most consistently for me.
Something wrong with the federation? The subscriber count for different communities also seem a whole lot lower here than on other Lemmy instances. https://lemmy.sdf.org/communities/listing_type/All/page/1 for example states that !Lemmy.world@lemmy.world only has 83 subscribers.
This is weird, I also can't access it directly via https://lemmy.sdf.org/c/loseit@discuss.tchncs.de, even though discuss.tchncs.de is a linked instance on lemmy.sdf.org. But I can access the community via another instance, for example https://lemmy.world/c/loseit@discuss.tchncs.de. I'm also new to the fediverse, so I don't know what the solution to this problem is.
Edit: Found a solution, see my other comment.
Having the same issue with some remote communities. I've been trying to access !chatt@feddit.nu for some time.
I can see it from https://feddit.nu/c/chatt ... agreed that it is not working. Weirdly, my original example is working now.
It's working now. I guess it was just a matter of time and syncing.
Got it.
Yes, it seems to be working now ... first try.
I think it can take a while for it to sync up after you do the initial search.
Fans of SDF