No, I can reach all of them (see also https://status.julialang.org/).
What does
julia> import Downloads
julia> Downloads.download("https://pkg.julialang.org/registries", stdout);
/registry/23338594-aafe-5451-b93e-139f81909106/34c1881b2d75b4e214fdfadab78996021ba487f7
return for you?