title: What is the very reason for WatchKit2 error code 7007 "session on paired device is not reachable"
body: <p>I am developing a glance view for my Apple WatchOS2 app. I'am currently didn't fully understand the prequisites for a stable WatchConnectivity connection now. I have the strange situation, that in the simulator my ComplicationController could successfully a sendMessage Request. When I try to look at my glance, the sendMessage request failed with: </p>
  
  <pre><code>Error Domain=WCErrorDomain Code=7007 
  "WatchConnectivity session on paired device is not reachable." 
  UserInfo={NSLocalizedDescription=WatchConnectivity session 
  on paired device is not reachable.
  </code></pre>
  
  <p>I have to admit, that I didn't start my app on the simulator. But why could the ComplicationController communicate and the WatchController won't. And I found no explanation about the error 7007 on the internet.</p>
  
  <pre><code>override func awakeWithContext(context: AnyObject?) {
      super.awakeWithContext(context)
  
      WCSession.defaultSession().sendMessage(["request": "getGlancesImages" ], replyHandler: {
          (result) -&gt; Void in
              self.processGetGlancesImages(result)
          }, errorHandler: { NSLog("WatchGlanceController2. \($0.description)") } )
  }
  </code></pre>
  
  <p>I am currently developing with WatchOS2 Beta 5 and iOS 9 Beta 5. I am fully aware, this is a beta but this is the last beta before release.</p>