Android Question Admob ads not appear in my app !

Dim adView1 As AdView

adView1.Initialize("Ad", "ca-app-pub-9767348470953371/5867461785")
    Activity.AddView(adView1, 0dip, 100%y-50dip, 100%x, 50dip)
    adView1.LoadAd

'This code will be applied to the manifest file during compilation.
'You do not need to modify it in most cases.
'See this link for for more information: http://www.b4x.com/forum/showthread.php?p=78136
AddManifestText(
<uses-sdk android:minSdkVersion="5" android:targetSdkVersion="14"/>
<supports-screens android:largeScreens="true"
    android:normalScreens="true"
    android:smallScreens="true"
    android:anyDensity="true"/>)
SetApplicationAttribute(android:icon, "@drawable/icon")
SetApplicationAttribute(android:label, "$LABEL$")
SetApplicationAttribute(android:theme, "@android:style/Theme.Holo")
'End of default text.

'AdMob
AddApplicationText(
<activity android:name="com.google.ads.AdActivity"
  android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"/>
)
'End of AdMob