Federation failing?
Since creating my hub, there have been a small handful of Mastodon instances that I can't connect to. One major one is meow.social. I've contacted the owner, and they whitelisted my outgoing IP and server agent, but noted that they haven't had any blocks on Cloudflare (which I'm using).
I couldn't find the server agent but I presumed it to be Hubzilla/10.4 (+https://hub.workersofthe.world)