Sample App ID Ad Load Error for Rewarded Ads

[AA]

When I tested loading ads using the sample app ID (ca-app-pub-3940256099942544/5224354917) with a rewarded ad, I encountered the following issue.
Note: When running with our app ID, ads load normally. (I watched the test ad because I registered as a test device on the AdMob web page.)


1) Run in debug mode
Error code:
{
  "Code" : 3,
  "Message" : "No fill.",
  "Domain" : "com.google.android.gms.ads",
  "Cause" : "null",
  "Response Info" : {
    "Response ID" : "null",
    "Mediation Adapter Class Name" : "",
    "Adapter Responses" : [ ],
    "Response Extras" : {
      "mediation_group_name" : "Campaign"
    }
  }
}
2) After registering the test device, I created an APK and installed and ran it. (I tested it on a device with an advertising ID reset.)
Code : List<String> testDeviceIds=Arrays.asList("Register the ID searched for in Logcat with setTestDeviceIds");

                    RequestConfiguration configuration=
                            new RequestConfiguration.Builder().setTestDeviceIds(testDeviceIds).build();
                    MobileAds.setRequestConfiguration(configuration);
Error code:
{
        "Code": 1,
        "Message": "Error building request URL: Too many recently failed requests for ad unit ID: ca-app-pub-3940256099942544/5224354917. You must wait a few seconds before making another ad request.",
        "Domain": "com.google.android.gms.ads",
        "Cause": "null",
        "Response Info": {
        "Response ID": "null",
        "Mediation Adapter Class Name": "",
        "Adapter Responses": [],
        "Response Extras": {}
}

Could you please let me know if you are still getting error 1 even though you used the sample app ID?