Android Studio Received status code 407 from server: Proxy Authentication Required

Question

I checked my proxy connection and it seems fine but I am getting this error :

Could not HEAD 'http://jcenter.bintray.com/com/android/tools/build/gradle/3.1.3/gradle-3.1.3.pom'. Received status code 407 from server: Proxy Authentication Required
Enable Gradle 'offline mode' and sync project

build.gradle has this content ;

buildscript {
    repositories {
        jcenter() {
            url "https://jcenter.bintray.com/"
        }
        maven { url 'http://maven.fabric.io/public' }
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
        classpath 'io.fabric.tools:gradle:1.+'

    }
}

If I directly click the link to the pom : http://jcenter.bintray.com/com/android/tools/build/gradle/3.1.3/gradle-3.1.3.pom

both on the Internet Explorer or Chrome I get this :

{
  "errors" : [ {
    "status" : 404,
    "message" : "Could not find resource"
  } ]
}

With this link open in the background :

https://repo.jfrog.org/artifactory/libs-release-bintray/com/android/tools/build/gradle/3.1.3/gradle-3.1.3.pom%27?referrer

I don't think this is the proxy error , rather the resource itself is not present in the URL reported.