Android gradle: https://maven.fabric.io/public not working with proxy

Question

Gradle project:

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        jcenter()
        maven { url 'https://maven.fabric.io/public' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.1.3'
        classpath 'io.fabric.tools:gradle:1.+'
    }
}
allprojects {
    repositories {
        jcenter()
        maven { url 'https://maven.fabric.io/public' }
    }

}

Gradle module:

apply plugin: 'com.android.application'
apply plugin: 'io.fabric'

android {
    // enter code
}

dependencies {
    // enter code
    compile('com.crashlytics.sdk.android:crashlytics:2.5.5@aar') {
        transitive = true
    }
}

I can't build gradle in android my project. Network with proxy. Android studio has set proxy.

Error:

Gradle sync failed: Cause: unable to find valid certification path to requested target.

Please...!
I am new begin Android.
Thanks so much!