Prod error on :sys.get_status, but dev is fine

I’m having an odd problem I don’t know how to debug. I have everything working smoothly in my dev environment, but after (my first, for this app) production build I couldn’t connect to the app. So I dig a little, and check :sys.get_status Myapp.Endpoint.Server as I normally would, but I get errors in the production console:

iex(myapp@> :sys.get_status Myapp.Endpoint.Server
** (exit) exited in: :sys.get_status(Myapp.Endpoint.Server)
** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
(stdlib) sys.erl:303: :sys.send_system_msg/2

but no errors in dev:

:sys.get_status Myapp.Endpoint.Server
{:status, #PID<0.348.0>, {:module, :gen_server},
 [["$initial_call": {:supervisor, Phoenix.Endpoint.Server, 1},
   "$ancestors": [Myapp.Endpoint, Myapp.Supervisor, #PID<0.320.0>]], :running,
  #PID<0.335.0>, [],
  [header: 'Status for generic server Elixir.Myapp.Endpoint.Server',
   data: [{'Status', :running}, {'Parent', #PID<0.335.0>},
    {'Logged events', []}],
   data: [{'State',
     {:state, {:local, Myapp.Endpoint.Server}, :one_for_one,
      [{:child, #PID<0.349.0>, {:ranch_listener_sup, Myapp.Endpoint.HTTP},
        {Phoenix.Endpoint.CowboyHandler, :start_link,
         [:http, Myapp.Endpoint,
          {:ranch_listener_sup, :start_link,
           [Myapp.Endpoint.HTTP, 100, :ranch_tcp,
            [max_connections: 16384, port: 4000], :cowboy_protocol,
            [env: [dispatch: [{:_, [],
                [{["phoenix", "live_reload", "socket", "longpoll"], [],
                   {Myapp.Endpoint, Phoenix.LiveReloader.Socket, :longpoll}}},
                 {["phoenix", "live_reload", "socket", "websocket"], [],
                   {Myapp.Endpoint, Phoenix.LiveReloader.Socket, :websocket}}},
                 {["socket", "websocket"], [], Phoenix.Endpoint.CowboyWebSocket,
                   {Myapp.Endpoint, Myapp.UserSocket, :websocket}}},
                 {:_, [], Plug.Adapters.Cowboy.Handler,
                  {Myapp.Endpoint, []}}]}]]]]}]}, :permanent, :infinity,
        :supervisor, [:ranch_listener_sup]}], :undefined, 3, 5, [], 0,
      Phoenix.Endpoint.Server, {:myapp, Myapp.Endpoint}}}],
   supervisor: [{'Callback', Phoenix.Endpoint.Server}]]]}

I have no build errors, or even warnings, and the console works fine, ping gives pong, etc. so I’m not sure what I would look at next since :sys.get_status is my typical debugging route… Any advice?

guessing, but check out prod.exs in config:

# ## Using releases
# If you are doing OTP releases, you need to instruct Phoenix
# to start the server for all endpoints:
#     config :phoenix, :serve_endpoints, true
# Alternatively, you can configure exactly which server to
# start per endpoint:
#     config :app_web, App.Web.Endpoint, server: true

so a config :phoenix, :serve_endpoints, true in prod.exs might do the deed.

Thanks for the rapid response! Sorry, I should have added that I tried that as well, but to no avail.

Incidentally, here is my prod.exs:

use Mix.Config

config :myapp, Myapp.Endpoint,
  http: [port: 4001],
  url: [host: ""],
  root: ".",
  cache_static_manifest: "priv/static/cache_manifest.json",
  server: true,
  version: Mix.Project.config[:version],
  secret_key_base: System.get_env("SECRET_KEY_BASE")

config :logger, level: :info

config :myapp, Myapp.Repo,
  adapter: Ecto.Adapters.Postgres,
  username: System.get_env("DB_PROD_USERNAME"),
  password: System.get_env("DB_PROD_PASSWORD"),
  database: System.get_env("DB_PROD_DATABASE"),
  size: 20 # The amount of database connections in the pool

Are you sure the application has been started and that the server is there?