Despite these communities existing, Boost doesn't load them directly. I can still see posts from them in Local view, but viewing the community directly doesn't work. This happens on multiple different instances.
The (SFW) community in the image is: !announcements@burggit.moe
burggit.moe/c/announcements
(I'm not sure which link style works, so I'm including both)
Could those communities be defederated?
Alternatively, if it's a small and new community, you might be the first person to try and load it. Maybe Boost can't handle that fetch. Try viewing the community with your account on desktop first
It can't be that it's defederated because I was using an account local to that instance. Plus, loading the community on a browser works fine.