Firebase Notification erro ao enviar notification

Após efetuar todas as configurações utilizando o Android Studio, tentei enviar uma notification através do site e o seguinte erro foi lançado:

06-15 09:37:46.806 14868-2021/br.com.alura.agenda E/AndroidRuntime: FATAL EXCEPTION: pool-2-thread-1
                                                                    Process: br.com.alura.agenda, PID: 14868
                                                                    java.lang.AbstractMethodError: abstract method "void com.google.firebase.iid.zzb.handleIntent(android.content.Intent)"
                                                                        at com.google.firebase.iid.zzc.run(Unknown Source)
                                                                        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
                                                                        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
                                                                        at java.lang.Thread.run(Thread.java:818)

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    defaultConfig {
        applicationId "br.com.alura.agenda"
        minSdkVersion 23
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    packagingOptions {
        exclude "META-INF/LICENSE"
    }
    productFlavors {
    }
}


dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.3.1'
    compile 'com.android.support:cardview-v7:25.3.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    compile 'com.android.support:design:25.3.1'
    compile 'com.google.android.gms:play-services-maps:11.0.0'
    compile 'com.google.android.gms:play-services-location:11.0.0'
    compile 'com.squareup.retrofit2:retrofit:2.3.0'
    compile 'com.squareup.retrofit2:converter-jackson:2.3.0'
    compile 'com.squareup.okhttp3:logging-interceptor:3.8.0'
    compile 'com.google.firebase:firebase-core:9.6.1'
    compile 'com.google.firebase:firebase-messaging:9.6.1'
    compile 'com.google.firebase:firebase-crash:9.6.1'
    testCompile 'junit:junit:4.12'
}


apply plugin: 'com.google.gms.google-services'