Seems like the ads work without this call. You can call it with:
B4X:
Dim ctxt As JavaObject
ctxt.InitializeContext
MobileAds.InitializeStatic("com.google.android.gms.ads.MobileAds")
MobileAds.RunMethod("initialize", Array(ctxt, YourAdMobAppId))
Best to do it in Activity_Create when FirstTime is True.
If FirstTime Then
Dim ctxt As JavaObject
ctxt.InitializeContext
Dim MobileAds As JavaObject
MobileAds.InitializeStatic("com.google.android.gms.ads.MobileAds")
MobileAds.RunMethod("initialize", Array(ctxt, "ca-app-pub-3940256099942544~3347511713")) 'Sample ID
End If
This is not still release to all users.
I talked with a Google account manager and he says that you will see this ads only if your account has a manager.