Google Adwords OAuth "error" : "invalid_client" exception

Question

I've inherited a google adwords project which is using OAuth 2.0 for Installed Applications to connect to the google adwords API.

I'm falling over on the first hurdle; I've downloaded the following example project from github;

https://github.com/googleads/googleads-dotnet-lib/tree/master/examples/AdWords/CSharp/OAuth

When I place all the details into the web.config as directed it doesn't work. I've put in;

the developer token
the customer Id
The refresh token.

This is all brand new to me, my understanding is that when using the refresh token the application should get a new access token and allow access to the API.

The above image shows the sample app interface, when I click on the "Get campaigns" link receive an exception message;

Google.Api.Ads.Common.Lib.AdsOAuthException was caught
  HResult=-2146233088
  Message=Failed to refresh access token.
{
  "error" : "invalid_client"
}
  Source=Google.Ads.Common
  StackTrace:
       at Google.Api.Ads.Common.Lib.OAuth2ProviderForApplications.RefreshAccessTokenInOfflineMode()
       at Google.Api.Ads.Common.Lib.OAuth2ProviderForApplications.RefreshAccessToken()
       at Google.Api.Ads.Common.Lib.OAuth2ProviderBase.RefreshAccessTokenIfExpiring()
       at Google.Api.Ads.Common.Lib.OAuth2ProviderForApplications.RefreshAccessTokenIfExpiring()
       at Google.Api.Ads.Common.Lib.OAuth2ProviderBase.GetAuthHeader()
       at Google.Api.Ads.Common.Lib.OAuth2ProviderForApplications.GetAuthHeader()
       at Google.Api.Ads.AdWords.Lib.AdWordsSoapClient.InitForCall(String methodName, Object[] parameters)
       at Google.Api.Ads.Common.Lib.AdsSoapClient.MakeApiCall(String methodName, Object[] parameters)
       at Google.Api.Ads.Common.Lib.AdsSoapClient.Invoke(String methodName, Object[] parameters)
       at Google.Api.Ads.AdWords.v201601.CampaignService.get(Selector serviceSelector)
       at Google.Api.Ads.AdWords.Examples.CSharp.OAuth.Default.OnGetCampaignsButtonClick(Object sender, EventArgs eventArgs) in c:\Adwords\examples\AdWords\CSharp\OAuth\Default.aspx.cs:line 130
  InnerException:

The application was using these credentials in a previous application, seemingly without issue.

I've searched high and low for an answer to this, the exception says that the access token can't be refreshed but the ambiguous reasoning doesn't help a great deal.

Could someone offer any further insight?

Many thanks.

Savas Adar Savas Adar · Accepted Answer · 2017-03-10T09:31:52

You should set OAuth2ClientId and OAuth2ClientSecret values in webconfig.

  <add key="OAuth2ClientId" value="your client id"/>
<add key="OAuth2ClientSecret" value="your client secret"/>

You can get clientid and client secret code from https://console.developers.google.com/project

Provide the OAuth2 client ID and secret. You can create one from https://console.developers.google.com/project. See https://developers.google.com/identity/protocols/OAuth2WebServer for more details.

Google Adwords OAuth "error" : "invalid_client" exception

1 Answers