When using a test ad unit I get "no ad config" on AdMob

Question

I've setup AdMob on Android to load a test ad unit ca-app-pub-3940256099942544/2247696110, this used to work fine before but now I'm getting an error. I think it is related to app-ads.txt, which is configured fine for my own ads but maybe it fails on the test ad units? Is there a way to get around this when using MoPub to mediate?

{
  "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": []
  }
}

Answer 1

I believe this solves the issue https://developers.google.com/admob/android/test-ads

You have to add an entry to your app-ads.txt

Answer 2

you just need to change the package name in build.gradle (app)

defaultConfig {
        applicationId "com.yourpacket.name"

Answer 3

Solution 1 : You should add a test device to your admob account to see ads on your phone.

Solution 2 : Change package name of your app

defaultConfig {
    applicationId "com.yourpacket.name"

Answer 4

If your app package name is exist in playstore then ad will now show it will give this error

To solve this error please change your package name.

Note: It may also happen someone already claimed given package name and that person's app is unpublished.