title: VSTS unable to load the service index for source 401
body: <p>I'm aware of the other posts about the same signature. I still can't resolve my issue after going thru them.</p>
  
  <p>My team uses VSTS's build definition for continuous integration. 
  <a href="https://i.stack.imgur.com/6VpzE.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/6VpzE.jpg" alt="enter image description here"></a></p>
  
  <p>This build definition works fine until the lastes pull request. 
  I'm running into the error msg below during the Nuget Restore</p>
  
  <blockquote>
    <p>2018-06-20T00:37:27.6438127Z System.AggregateException: One or more errors occurred. ---> NuGet.Protocol.Core.Types.FatalProtocolException: Unable to load the service index for source <a href="https://microsoft.pkgs.visualstudio.com/_packaging/CBT/nuget/v3/index.json" rel="noreferrer">https://microsoft.pkgs.visualstudio.com/_packaging/CBT/nuget/v3/index.json</a>. ---> System.Net.Http.HttpRequestException: Response status code does not indicate success: 401 (Unauthorized).</p>
  </blockquote>
  
  <p>I do have <a href="https://microsoft.pkgs.visualstudio.com/_packaging/CBT/nuget/v3/index.json" rel="noreferrer">https://microsoft.pkgs.visualstudio.com/_packaging/CBT/nuget/v3/index.json</a> in the nuget.config, and there is <strong>nothing changed</strong> in the nuget.config in the failing PR</p>
  
  <p>I can nuget restore and build the entire solution successfully on my local machine using VS2017. The only related change in the PR is that instead of using package.config, it uses packagereference to get the nuget package. I tried to move back to using package.config, the build would still fail with the same error msg.</p>
  
  <p>Thanks in advance.</p>