Response status code does not indicate success: 401 Tumblr
<p>I want to implement authorization to Tumblr.
During the reception  access_token like this:</p>

<pre><code>string request_url =
                 "https://www.tumblr.com/oauth/access_token" + "?" +
                 "oauth_consumer_key=" + oauth_consumer_key + "&amp;" +
                 "oauth_token=" + main_oauth_token + "&amp;" +
                 "oauth_signature_method=" + "HMAC-SHA1" + "&amp;" +
                 "oauth_signature=" + Uri.EscapeDataString(oauth_signature) + "&amp;" +
                 "oauth_timestamp=" + oauth_timestamp + "&amp;" +
                 "oauth_nonce=" + oauth_nonce + "&amp;" +
                 "oauth_version=" + "1.0" + "&amp;" +
                 "oauth_verifier=" + oauth_verifier;

                HttpClient httpClient = new HttpClient();
                string responseBodyAsText = await httpClient.GetStringAsync(request_url);
</code></pre>

<p>I get the following error:</p>

<blockquote>
  <p>An exception of type 'System.Net.Http.HttpRequestException' occurred in mscorlib.ni.dll but was not handled in user code</p>
  
  <p>Additional information: Response status code does not indicate
  success: 401 (Unauthorized).</p>
</blockquote>

<p>Callback URL i am set. What could be the problem?</p>