The webconsole of Rails is a very useful tool for debugging purpose.
If you use inside a docker container you cant use it for security/network reason.

If you want to use it again you have to add this simple line in your application.rb

if Rails.env.development?
  config.web_console.whitelisted_ips = ['172.16.0.0/12', '192.168.0.0/16']
end