How to set and verify cookie with a custom domain on heroku?

Question

I'm not even sure that's the right question.

I set up ActionCable to open a websocket connection, and it works great on heroku, if it's just the app-name.herokuapp.com But when I try to use the custom domain set up for the app, the connection is not verified.

So, I'm trying to set a cookie on the client, to be able to verify the user

channels/application_cable/connection.rb

module ApplicationCable  
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = find_verified_user
      logger.add_tags 'ActionCable', current_user.email
    end

    protected
      def find_verified_user # this checks whether a user is authenticated with devise
        if cookies.signed['user.id']
          verified_user = User.find_by(id: cookies.signed['user.id'])
          verified_user
        else
          reject_unauthorized_connection
      end
    end
  end
end

On example.com - it keeps comning back as an unauthorized connection. But app-name.herokuapp.com is connectiong fine.

initializers/warden_hooks.rb

Warden::Manager.after_set_user do |user,auth,opts|
  scope = opts[:scope]
  auth.cookies.signed["#{scope}.id"] = user.id
end

I try to allow calls from both herokuapp.com and example.com: environments/production.rb

Rails.application.configure do
  config.action_cable.url = 'wss://app-name.herokuapp.com//cable'
  config.action_cable.allowed_request_origins = [ 'https://www.example.com', /http:\/\/www.example.com.*/, 'https://app-name.herokuapp.com', /http:\/\/app-name.herokuapp.com.*/ ]
end

Why is it unverified on the custom domain? How can I set a cookie variable to verify it? What am I misunderstanding about this concept?

Thanks!

PS.Before someone trys to add as an "answer" -- YES I changed the name to example.com and app-name.herokuapp.com for this post, and NO it doesnt actually say that in my code :)