Ruby on Rails

Have someone worked with Google AdWords API ?

I'm using

• devise
• omniauth
• omniauth-google-oauth2
• google-adwords-api

I'm getting the token from oauth callback:

class OmniauthCallbacksController < Devise::OmniauthCallbacksController    def google_oauth2      session[:token] = request.env["omniauth.auth"].credentials      ...    end  end

and following the example of adwords on rails to get api instance:

 def adwords_api     @api ||= create_adwords_api   end     def create_adwords_api     api = AdwordsApi::Api.new Rails.application.config_for(:adwords)       token = session[:token]     if token       credentials = api.credential_handler       credentials.set_credential :oauth2_token, token       credentials.set_credential :client_customer_id, current_user.id     end     api   end

but when I try to get campaigns, It returns an error: [AuthenticationError.OAUTH_TOKEN_HEADER_INVALID @ ; trigger:'<null>'

and based on the log, this is the url of request:
[2015-01-09T10:12:44.237172 #6481] DEBUG -- : SOAP request: https://adwords.google.com/api/adwords/cm/v201409/CampaignService

How can I fix this?