The servers need a bit of time to sync up, especially with these new communities. I am keeping a small text doc to try again later with when they don't work. The more people participate, the more the servers will "talk" and sync. It's early growing pains. I noticed it on Mastodon, but it sped up after more people joined.
It doesn't for me (from lemmy.sdf.org). Odd thing going on here.
In general with Lemmy I don't understand why links to communities can't open in your local webapp. The little dance of navigating through search seems like it shouldn't be necessary technically.