title: Microsoft Graph Subscriptions - Not receiving calendar events notifications
body: <p>We are using a multitenant application.
  We created a subscription to listen to calendar events for a particular user, but we are not receiving the notifications.</p>
  
  <p>The user accepted the following scopes: <code>Calendars.Read Calendars.ReadWrite Calendars.Read.Shared Calendars.ReadWrite.Shared offline_access User.Read.All</code></p>
  
  <p>When we call to POST <code>https://graph.microsoft.com/v1.0/subscriptions</code>
  BODY:</p>
  
  <pre><code>{  
  "resource": "/users/31c61efc-bc28-4552-9f0d-1a8735767c4e/calendars/AAMkAGRjZjY3OGRmLWU3MjAtNGExYy1hOTk0LTNkNjExOWVhZmYyNQBGAAAAAAD3yBF0B84VRJLe9CCZ4-ajBwDf5J1F10FqQ6VkC14neUWZAAAAAAEGAADf5J1F10FqQ6VkC14neUWZAABEL_2XAAA\u003d/events",  
  "changeType": "created,updated,deleted",  
  "clientState": "XXXXXX",  
  "notificationUrl": "https://XXXXX.ngrok.io/notification/event",  
  "expirationDateTime": "2019-05-31T14:42:08.651Z"
  }
  </code></pre>
  
  <p>Then the notificationUrl is called and we receive the validation token:
  <code>Validation: Testing client application reachability for subscription Request-Id: 9d020355-7589-4485-ba29-62d1ec899723</code></p>
  
  <p>But when we login into the <code>31c61efc-bc28-4552-9f0d-1a8735767c4e</code> account and update or create an event, no notification is beign sent.</p>
  
  <p>If we call to GET <code>https://graph.microsoft.com/v1.0/subscriptions</code> the subscription is created:</p>
  
  <pre><code>{
      "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#subscriptions",
      "value": [
          {
              "id": "b92d909e-b1b5-49b8-af54-74b7956d6565",
              "resource": "/users/31c61efc-bc28-4552-9f0d-1a8735767c4e/calendars/AAMkAGRjZjY3OGRmLWU3MjAtNGExYy1hOTk0LTNkNjExOWVhZmYyNQBGAAAAAAD3yBF0B84VRJLe9CCZ4-ajBwDf5J1F10FqQ6VkC14neUWZAAAAAAEGAADf5J1F10FqQ6VkC14neUWZAABEL_2XAAA=/events",
              "applicationId": "XXXX",
              "changeType": "created,updated,deleted",
              "clientState": null,
              "notificationUrl": "https://XXXX.ngrok.io/notification/event",
              "expirationDateTime": "2019-05-31T14:42:08.651Z",
              "creatorId": "31c61efc-bc28-4552-9f0d-1a8735767c4e"
          }
      ]
  }
  </code></pre>
  
  <p>Monitoring the ngrok calls, there is no failing call to the notification events endpoint.</p>
  
  <p>Is there any console log we can verify to understand what the problem could be?</p>
  
  <p>We tried to create subscriptions for different accounts with no success.
  We also tried to subcribe to <code>/me/events</code></p>