Why is butterknife 9.0.0-SNAPSHOT not resolving?

Please note that Butterknife has now reached 10.1.0 and there's no longer need for SNAPSHOT versions or any other maven libraries. AndroidX migration works as a charm. Just include:

dependencies {
    implementation 'com.jakewharton:butterknife:10.1.0'
    annotationProcessor 'com.jakewharton:butterknife-compiler:10.1.0'
}

or, if for some reason you're combining Kotlin and butterknife, replace annotationProcessor with kapt.

For more information, visit: https://github.com/JakeWharton/butterknife

UPDATE: You can now simply use ButterKnife 9-rc02 instead of the above mentioned solutions:

...
dependencies {
    implementation 'com.jakewharton:butterknife:9.0.0-rc2'
    annotationProcessor 'com.jakewharton:butterknife-compiler:9.0.0-rc2'
...

---

Based on the answer from Naveen, the solution is here.
However, there are missing details. Please refer the below Gradle configurations for the complete solution:

buildscript {
    repositories {
        jcenter()
        google()
        maven { url "https://jitpack.io" }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.0-alpha10'
    }
}

allprojects {
    repositories {
        jcenter()
        google()
        maven { url "https://jitpack.io" }
        mavenCentral()
        maven {
            name 'Sonatype SNAPSHOTs';
            url 'https://oss.sonatype.org/content/repositories/snapshots/'
        }
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

and

...
dependencies {
    implementation 'com.jakewharton:butterknife:9.0.0-SNAPSHOT'
    annotationProcessor 'com.jakewharton:butterknife-compiler:9.0.0-SNAPSHOT'
...

Basically, don't use apply plugin: 'com.jakewharton.butterknife' and classpath 'com.jakewharton:butterknife-gradle-plugin:9.0.0-SNAPSHOT' from the suggestion here.

Also, this Android Studio Settings > Compiler configuration: