Ad failed to load: 3

Good afternoon, I am try to implement ads in my application but my real AD does not appear, only test AD, in the admob tab it appears that more than 300 requests were made, and there is no ads in the application. Is it necessary for me to publish my app in the play store so that the ads start to appear? And my account has been verified for a long time. In my Logcat appear this error Ad failed to load: 3, what i needed to do , to the ads start to showing?
page admob

Logcat

As per the Documentation you are getting the following error code:

> public static final int ERROR_CODE_NO_FILL
>
> The ad request was successful, but no ad was returned due to lack of
> ad inventory.
>
> Constant Value: 3

> If you are getting this error, then your code is correct. The issue is
> that AdMob does not always have an ad to return for every request.
> This may happen particularly if you have just registered your AdMob
> publisher ID, as it takes some time and multiple requests before the
> new ID starts returning ads.
>
> I also faced the same issue. My app was showing test ads, but not real one.
> In my case ads started showing up when I uploaded my app to Google Play.
>
> To confirm your app shows ads correctly, you may first add your app to test tracks first.

Error code 3 means your implementation is correct but your app is not approved by google admob,so you have to submit your app for approval, once your app is approved than your app will start receiving ad after 24 hrs and you have to setup your payment method in google admob.

you can submit your app through this link for approval:
https://support.google.com/admob/contact/android_APK_submission?hl=en

If you are using app-ads.txt for your app, then you also have to include this line in your app-ads.txt file in order to load ads using the demo ad units:

google.com, pub-3940256099942544, DIRECT, f08c47fec0942fa0

Here the official Google AdMob reference: https://developers.google.com/admob/android/test-ads

It shows when your device is not connected with Test Mode in your AdMob account. Connect your device with test mode and try this error will resolve.

https://apps.admob.com/v2/settings/test-devices/list?_ga=2.248138183.156733708.1671428691-2046682952.1670650994&_gac=1.127285631.1670650998.Cj0KCQiA1sucBhDgARIsAFoytUvUl2cXmiqt4eGOJlPz7EOFYJxnbpcLX3uIEhk71c3oHZ3BxMsgBE0aAlkcEALw_wcB&_gl=11ubza84_gaMjA0NjY4Mjk1Mi4xNjcwNjUwOTk0_ga_6R1K8XRD9P*MTY3MTQyODY5MS40LjAuMTY3MTQyODY5MS4wLjAuMA..