I’m trying to connect a remote shell to a running GAE elixir app. The app is running fine, when I try to connect I get this:

Could not contact remote node the_kraken@aef-default-20200421t125549-782j.europe-west2-b.c.quick-cogency-270011.internal, reason: :nodedown. Aborting...

I am using mix releases, the hostname is correct AFAICT because it comes from a request to google. How can I get more info about what nodedown means?

My env.sh.eex looks like this if that helps:

#!/bin/sh

# Set the release to work across nodes. If using the long name format like
# the one below (my_app@127.0.0.1), you need to also uncomment the
# RELEASE_DISTRIBUTION variable below. Must be "sname", "name" or "none".
export RELEASE_DISTRIBUTION=name
export RELEASE_NODE=<%= @release.name %>@${HOSTNAME}
export RELEASE_COOKIE=${NODE_COOKIE}

When should NODE_COOKIE be set?

Thanks!