title: Update a OneNote page using Graph API
body: <p>I am trying to update a OneNote page using the <code>PATCH</code> request through the Microsoft Graph API. I keep getting <code>Error 19999</code> which according to this <a href="https://msdn.microsoft.com/en-us/office/office365/howto/onenote-error-codes" rel="nofollow noreferrer">https://msdn.microsoft.com/en-us/office/office365/howto/onenote-error-codes</a> means "Unknown Error"</p>
  
  <pre><code>var pageId = settings.DefaultPage;
  string requestUrl = $"https://graph.microsoft.com/v1.0/me/onenote/pages/{pageId}/content";
  string body = @"{ 
  {
  'target':'body',
  'action':'append',
  'position':'after',
  'content':'&lt;div&gt; added new &lt;/div&gt;'}}";
  var content = new StringContent(body, Encoding.UTF8, "application/json");
  HttpRequestMessage req = new HttpRequestMessage()
  {
      Method = new HttpMethod("PATCH"),
      Content = content,
      RequestUri = new Uri(requestUrl)
  };
  HttpClient client = new HttpClient()
  {
      BaseAddress = new Uri(requestUrl),
  };
  client.DefaultRequestHeaders.TryAddWithoutValidation("authorization", "Bearer " + settings.MsaAccessCode);
  HttpResponseMessage response = await client.SendAsync(req);
  </code></pre>
  
  <p>I can verify that the Authorization Code is valid (as I am able to do other actions like creating a new page) and has the necessary scopes to update a page. Can anyone help me with identifying the problem here?</p>