title: How long does it take for an AdMob Ad unit ID to become active?
body: <p>I created a new Ad unit ID around 4 hours ago and started using it in the release build of my unreleased Android app. But all I get is a blank view and the following logcat output:</p>
  
  <pre><code>W/Ads: Received error HTTP response code: 400
  W/Ads: There was a problem getting an ad response. ErrorCode: 0
  W/Ads: Failed to load ad: 0
  </code></pre>
  
  <p>Since the the Ad unit IDs for the other apps in the same AdMob account work - even when used in the app in question - the best explanation I can come up with is that the new ID hasn't been activated or properly propagated yet.</p>
  
  <p>How long does this usually take or what am I missing?</p>