Take a look at this post: Could not contact remote node reason: :nodedown. Aborting... - #7 by Mark
There’s some notes about:
ENV ECTO_IPV6 true
ENV ERL_AFLAGS "-proto_dist inet6_tcp"
also some stuff about the rel folder ( env.ssh.eex file, etc), which has some release files. The Legacy docs talk about that here: Legacy pre v1.6.3 Phoenix App · Fly Docs
One other thing that has helped me is to compare my project to the existing hello_elixir repo to see what is different: