Flutter MissingPluginException(No implementation found for method loadInterstitialAd on channel plugins.flutter.io/firebase_admob)

Error that I am getting. I have seen other MissingPluginExeptions, but none for firebase_admob.

[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: MissingPluginException(No implementation found for method loadInterstitialAd on channel plugins.flutter.io/firebase_admob)
#0      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:319:7)
<asynchronous suspension>                                               
#1      _invokeBooleanMethod (package:firebase_admob/firebase_admob.dart:611:61)
#2      _AsyncAwaitCompleter.start (dart:async-patch/async_patch.dart:45:6)
#3      _invokeBooleanMethod (package:firebase_admob/firebase_admob.dart:610:34)
#4      InterstitialAd.load (package:firebase_admob/firebase_admob.dart:377:12)
#5      _personSettingsState.initState (package:randompersonapp/personSettings.dart:68:45)
#6      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4355:58)
#7      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
#8      Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
#9      Element.updateChild (package:flutter/src/widg<…> 

These are the processes I have tried. I get no errors from the flutter doctor.

flutter clean
flutter doctor
flutter run

This is the code I am using to get the error. It is inside a stateful widget, but I can't show all of it because it is in production code.

import 'dart:math';

import 'package:firebase_admob/firebase_admob.dart';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';


InterstitialAd myInterstitial;

  InterstitialAd buildInterstitialAd() {
    return InterstitialAd(
      adUnitId: InterstitialAd.testAdUnitId,
      listener: (MobileAdEvent event) {
        if (event == MobileAdEvent.failedToLoad) {
          myInterstitial..load();
        } else if (event == MobileAdEvent.closed) {
          myInterstitial = buildInterstitialAd()..load();
        }
        print(event);
      },
    );
  }

void showInterstitialAd() {
    myInterstitial..show();
  }

  void showRandomInterstitialAd() {
    Random r = new Random();
    bool value = r.nextBool();

    if (value == true) {
      myInterstitial..show();
    }
  }

@override
  void initState() {
    myInterstitial = buildInterstitialAd()..load();

    super.initState();
  }

  @override
  void dispose() {
    myInterstitial.dispose();

    super.dispose();
  }

I have made two apps in firebase and linked them with the app id in the appmanifest for Android and info.plist for IOS. The Error points to the line

myInterstitial = buildInterstitialAd()..load();

Anyone have any tips? I am open to any suggestions or thoughts on the matter.

if you are with this problem: First: add this in android manifest

<manifest>
    <application>
        <!-- Sample AdMob App ID: ca-app-pub-3940256099942544~3347511713 -->
        <meta-data
            android:name="com.google.android.gms.ads.APPLICATION_ID"
            android:value="[ADMOB_APP_ID]"/>
    </application>
</manifest>

Second: When you add something in android manifest, you need close the app (stop the simulation) and start again to android manifest refresh.

PS: do not forget to add this in app/build.gradle:

implementation 'com.google.firebase:firebase-ads:18.0.0'