Android Question NativeExpressAd failed with ErrorCode 0

Sub Globals
   Private adview1 As NativeExpressAd
End Sub

Sub Activity_Create(FirstTime As Boolean)
   adview1.Initialize("Ad", "ca-app-pub-126757084444444/44444444", 100%x, 200dip) 'change the ad unit id
   Activity.AddView(adview1, 0, 0,  100%x, 200dip)
   adview1.LoadAd
End Sub


Sub Ad_FailedToReceiveAd (ErrorCode As String)
  Log("failed: " & ErrorCode)
End Sub
Sub Ad_ReceiveAd
  Log("received")
End Sub
Sub Ad_AdScreenDismissed
   Log("Dismissed")
End Sub
Sub Activity_Pause (UserClosed As Boolean)
   adview1.Pause
End Sub

Sub Activity_Resume
   adview1.Resume
End Sub