Android Studio: Gradle Refresh Failed – Could not find com.android.tools.build:gradle:2.2.0-alpha6

This is because the build process is unable to find the dependency in Maven repository. Add jcenter() along with mavenCentral() in your project level build.gradle file.

buildscript {
    repositories {
        mavenCentral()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.2.0'
    }
}