PHP Android WWW Unknown Error

So I am getting issues with my login/registration system when deploying to Android. If I run it in Unity it works just fine. But when I run it in Android I keep getting Unknown Error when submitting POST requests to my PHP back-end. This is coming from parsing www.error. www.text comes back empty. So I simplified the code to test, and I STILL get Unknown Error even with this super simple code. Any ideas?

Clickme.cs

using System.Collections;
using UnityEngine;
using UnityEngine.UI;

public class Clickme : MonoBehaviour
{
    public Text Result;

	public void OnClick()
    {
        StartCoroutine(RunScript());
    }

    IEnumerator RunScript()
    {
        WWW www = new WWW("http://www.familypolaris.com/helloWorld.php");
        yield return www;

        if (www.text == "")
            Result.text = "Result was empty, error: " + www.error;
        else
            Result.text = www.text;
    }
}

helloWorld.php

<?php
    echo "Hello World!";
?>

I figured it out, so I will post the answer here. After somebody commented that they tried my code and it worked just fine, I decided to try another device here. That device also failed to register and login. This told me something was wrong with my build settings. My first idea was to switch build type from Gradle to Internal, and that solved the problem for both my devices immediately.