Rails mount twice in routes.rb

I need to mount two times in my routes.rb file. Since I added ForestLiana, the second one (Facebook Messenger) is not working.

Any idea how I can solve this issue and use both?

Rails.application.routes.draw do
  mount ForestLiana::Engine => '/forest'
  resources :cards
  resources :bot_users
  resources :core_bots
  resources :letters
  devise_for :users, :controllers => { :omniauth_callbacks => "users/omniauth_callbacks", registrations: 'registrations' }

  mount Facebook::Messenger::Server, at: 'listen'
end