title: facebook ads not showing on android device
body: <p>I use facebook ads in my android apps.I found that some test devices never show ads,no matter banner or interstitial.I wonder why and try to find the reason but it doesn't log any info and call the 'onError' method.Finally I found the common place between these devices is that these devices don't have facebook app installed on it.Then I try to install facebook app and then login.The ads really show up.I'm confused why this happen.</p>
  
  <p>Is it necessary for facebook ads that facebook app must be installed?</p>