Exq_ui in production - issue

I am trying to run exq and exq_ui in my prod environment, I am getting the following error -

{:info, ["Application ", “exq_ui”, " exited: " | “exited in: ExqUi.start(:normal, )\n ** (EXIT) exited in: GenServer.call(ExqUi.Api, :queue_size, 5000)\n ** (EXIT) time out”], {{2019, 8, 5}, {12, 17, 6, 180}}, [module: :application_controller, function: “info_exited/3”, file: “application_controller.erl”, line: 1941]}

my config for exq and exq_ui is as follows -

config :exq,
  name: Exq,
  host: "<host>",
  port: 6979,
  password: "<password>",
  database: 20,
  namespace: "exq",
  concurrency: 20,
  queues: [<queues>],
  poll_timeout: 50,
  scheduler_poll_timeout: 200,
  scheduler_enable: true,
  max_retries: 0,
  shutdown_timeout: 5000,
  start_on_application: false

config :exq_ui,
  web_port: 4040,
  web_namespace: "",
  server: true

The application is not starting and is throwing the above error.
Can someone please help me out in figuring out the issue.