title: Google IMA iOS SDK `IMAAdsLoader -requestAdsWithRequest:` doesn't work on the 2nd time
body: <p>I am using GoogleAds-IMA-iOS-SDK (3.3.1) via Cocoapods to show video ads, Xcode 8.0. This is how I set up the adsLoader. Note I have <code>enableDebugMode = true</code>. This adsLoader is stored in <code>VKSharedAdManager.adsLoader</code> for reuse.</p>
  
  <pre><code>IMASettings *settings = [[IMASettings alloc] init];
  settings.ppid = @"IMA_PPID_0";
  settings.enableDebugMode = true;
  settings.language = kLanguageCodeEnglish;
  self.adsLoader = [[IMAAdsLoader alloc] initWithSettings:settings];
  </code></pre>
  
  <p>Then I make the request with that loader. </p>
  
  <pre><code>IMAAdDisplayContainer *displayContainer = [[IMAAdDisplayContainer alloc] initWithAdContainer:self.adRequest.adContainer companionSlots:nil];
      self.request = [[IMAAdsRequest alloc] initWithAdTagUrl:adTagUrl adDisplayContainer:displayContainer contentPlayhead:VKSharedAdManager.contentPlayhead userContext:nil];
      VKSharedAdManager.adsLoader.delegate = self;
      DDLogVerbose(@"%@: requesting %@", self, adTagUrl);
      [VKSharedAdManager.adsLoader requestAdsWithRequest:self.request];
  </code></pre>
  
  <p>The first ads works fine, <code>IMAAdsLoaderDelegate</code> methods are called fine. The IMA loader debug log is as follows. (There are more but this is the beginning...)</p>
  
  <pre><code>2016-12-13 15:35:14.769 MyApp[5835:1419742] Core: (INFO) ima.loader.AdsLoaderWrapper: Requesting ads using new ads loader.
  2016-12-13 15:35:14.963 MyApp[5835:1419742] Core: (INFO) ima.loader.AdsLoaderWrapper: requestAds, processing external request.
  2016-12-13 15:35:14.964 MyApp[5835:1419742] Core: (INFO) ima.loader.SequentialAdsLoader: Enqueued new request.
  2016-12-13 15:35:14.965 MyApp[5835:1419742] Core: (INFO) ima.loader.SequentialAdsLoader: Starting request from queue.
  2016-12-13 15:35:15.257 MyApp[5835:1419742] Core: (INFO) ima.loader.AdSourceFetcher: Creating PlaylistSource.
  2016-12-13 15:35:15.271 MyApp[5835:1419742] Core: (INFO) ima.loader.AdsLoaderWrapper: dispatchPlaylist_
  ...
  ...
  </code></pre>
  
  <p>Next, I close that video and then play another video. 
  <strong>PROBLEM:</strong> Now the log just show this and nothing happens.</p>
  
  <pre><code>2016-12-13 15:37:59.266 MyApp[5835:1419742] Core: (INFO) ima.loader.AdsLoaderWrapper: Requesting ads using new ads loader.
  </code></pre>
  
  <p>Then for all next videos after there's no log at all. If I restart the app, then same thing happen. Only the first ad works. I have tried like 10+ times and there's one lucky time that it will work for all videos. All testing is done on iPad mini device with iOS 9.3.5. I'm not sure what's wrong.</p>