Ads not showing for correct app package name

Live ads from Google Ad Manager are not showing on correct app package name (eg. com.android.test) and returns the error below

{
      "Code": 3,
      "Message": "No ad config.",
      "Domain": "com.google.android.gms.ads",
      "Cause": "null",
      "Response Info": {
        "Response ID": "null",
        "Mediation Adapter Class Name": "",
        "Adapter Responses": []
      }
}

Testing ad units ID are showing fine with no issue, but strangely if I changed my app package name to others like com.android.test.dev or com.android.test.staging the live ads will be shown without any issue as well.

I have seen a few people that has faced the same issue but it doesn't really help

https://groups.google.com/g/google-admob-ads-sdk/c/xhwxgDyu5Ds/m/X09ha2L4AQAJ

https://groups.google.com/g/google-admob-ads-sdk/c/Og5Gai4Vt4g/m/I4ZVM99qBQAJ

I am only using Google Ad Manager SDK 'com.google.android.gms:play-services-ads:19.7.0', not using AdMob

Thank you in advance!

After contacting Google Ads support, the reason behind this is due to our app is targeting kids age 6 - 12

The app will need to comply to this policy Tag a site or ad request for child-directed treatment https://support.google.com/admanager/answer/4442399?hl=en

In the app, we'll need to setTagForChildDirectedTreatment to true and maxAdContentRating to G in MyApplication, can refer to this link https://support.google.com/admanager/answer/9467073?hl=en#zippy=%2Ccode-sample-for-implementation-in-apps-for-everyone-including-children-and-families

 MobileAds.initialize(this)
 val config = MobileAds.getRequestConfiguration().toBuilder()
        .setTagForChildDirectedTreatment(TAG_FOR_CHILD_DIRECTED_TREATMENT_TRUE)
        .setMaxAdContentRating(MAX_AD_CONTENT_RATING_G).build()
 MobileAds.setRequestConfiguration(config)

Hope this is helpful to everyone facing the same issue.