Google Adword Oauth Error: Failed to refresh access token.

[Mahesh Kafaltiya]

            Hi, I am getting  following error ,while  refreshing my OAUTH access token for each google adwords sub clients. I have started getting them very frequently now. Please suggest if I am doing anything wrong?

ApiVersion: v201406 (lib18.3) 

     Google.Api.Ads.Common.Lib.AdsOAuthException: Failed to refresh access token.

{

  "error" : "internal_failure"

}

       Code Snippest:

            AdWordsAppConfig adWordsAppConfig = new AdWordsAppConfig();

            OAuth2ProviderForApplications oAuth2Provider = new OAuth2ProviderForApplications(adWordsAppConfig);

            // isOffline is required for installed application

            oAuth2Provider.IsOffline = true;

            oAuth2Provider.RefreshAccessTokenIfExpiring(); // this method causing exception.

            AdWordsUser user = new AdWordsUser(headers);

            user.OAuthProvider = oAuth2Provider;

            return user;