Google Analytics API 3 - Error:“invalid_grant”, Description:“”, Uri:“”

Question

I've 'googled' the life out of this issue today with zero resolve!

I am trying to build a very simple Google Analytics data request console app using a Service account. I have set up all the required details in the Google Developers Console but I am getting the following error:

An unhandled exception of type 'Google.Apis.Auth.OAuth2.Responses.TokenResponseException'          
occurred in Google.Apis.dll

Additional information: Error:"invalid_grant", Description:"", Uri:""

Below is the code in my console app (with keys hidden):

using System.Security.Cryptography.X509Certificates;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Analytics;
using Google.Apis.Analytics.v3;
using Google.Apis.Analytics.v3.Data;
using System;

namespace GoogleAnalyticsAPI
{

public class Program
{

    public static void Main(string[] args)
    {

        string profileId = "12345678";
        string serviceAccountEmail = "123456789abcdefghijklmnopq@developer.gserviceaccount.com";
        X509Certificate2 certificate = new X509Certificate2(@"PrivateKey.p12", "mypassword", X509KeyStorageFlags.Exportable);

        // Create credentials
        ServiceAccountCredential credential = new ServiceAccountCredential(
           new ServiceAccountCredential.Initializer(serviceAccountEmail)
           {
               Scopes = new[] { AnalyticsService.Scope.Analytics }
           }.FromCertificate(certificate));

        // Create the service
        var service = new AnalyticsService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = "Google Analytics API"

        });

        string startDate = "2014-07-01";
        string endDate = "2010-07-31";


        DataResource.GaResource.GetRequest request = service.Data.Ga.Get(string.Format("ga:{0}", profileId), startDate, endDate, "ga:visits, ga:newVisits");
        request.Dimensions = "ga:city";
        GaData data = request.Execute();

    }

}
}

Any help here would be greatly appreciated!

Note, here are some sources I've followed:

Tutorial Followed to get above code

Useful but out of date

Google's code walk through - not in C# .Net

Answer 1

It turns out I had the wrong credentials, if anyone else has the same problem:

1. Double check you're using the service account email ending "@developer.gserviceaccount.com"
2. Check the downloaded .p12 file is located in your debug folder and you supply the correct private key password (given to you when you create your service account).