I add the extra information you gave as advised.
AdRequest request = new AdRequest.Builder()
.AddExtra("is_designed_for_families", "true")
.TagForChildDirectedTreatment(true)
.Build();
The only difference is I am using banner and their one is using Interstitial ad
I just wonder whether the type of interstitial is better than normal banner.
Btw thanks for the support team link, I may just pop a question in there for them to help me.
cheers
andy