We use ruby on rails, there is no SDK for ruby on rails, these snippets are copy & pasted from our code base and should be edited before reproducing the issue.

The perform method calls all subsequent calls .

It first fetches the user_id which is used to check what pages the user has given us access to.

It then fetches the page_access_tokens for all the accessible pages.

It then loops through the pages and subscribes to the webhooks

def perform
  @user_id = get_user_id
  @pages = get_page_access_tokens
  @pages.each do |page|
    @facebook.subscribe_to_webhook(page[:id], page[:token])
    token = @facebook.get_long_lived_access_token(page[:token])
    options = {
      ad_account_id: @ad_account_id
    }

    @access_token ||= @organization.access_tokens.create!(token: token, options: options, name: 'Meta', user_id: @user_id)
  end
  @access_token
end


def get_page_access_tokens(user_id, access_token)
  response = Faraday.get("#{ENV.fetch('FACEBOOK_GRAPH_API')}/#{user_id}/accounts") do |req|
    req.headers['Content-Type'] = 'application/json'
    req.params['access_token'] = access_token
  end

  raise "Unable to get page access token server responded with #{response.body} and status #{response.status}" unless response.success?

  data = JSON.parse(response.body)
  page_data = data['data']
  page_data.map { |page| { id: page['id'], name: page['name'], token: page['access_token'] } }
end

def subscribe_to_webhook(page_id, page_token)
  response = Faraday.post("#{ENV.fetch('FACEBOOK_GRAPH_API')}/#{page_id}/subscribed_apps?subscribed_fields=leadgen") do |req|
    req.headers['Content-Type'] = 'application/json'
    req.params['access_token'] = page_token
    req.body = {
      override_callback_uri: "#{ENV.fetch('API_URL')}/facebook/webhooks/#{@organization['id']}",
      verify_token: {local_token}
    }.to_json
  end

  raise "Unable to subscribe to leadgen webhook server responded with #{response.body} and status #{response.status}" unless response.success?
  response
end

def get_user_id(access_token)
  response = Faraday.get("#{ENV.fetch('FACEBOOK_GRAPH_API')}/me") do |req|
    req.headers['Content-Type'] = 'application/json'
    req.params['fields'] = 'id'
    req.params['access_token'] = access_token
  end

  raise "Unable to get user id server responded with #{response.body} and status #{response.status}" unless response.success?
  JSON.parse(response.body)['id']
end

I'm still stuck with this issue.