Hello,
just add "file:///" at the beginning at the url works for me on 2018.1 !

Same problem as reported in previous post by METGEMAY 18, 2017

re. www.GetAudioClip(false, true, AudioType.OGGVORBIS

Running on running on IOS (11.3.1) on the iPad Generation 5
built with Unity v. 2018 1.0f2 (d4d99f31acba) Personal.
(using Google Resonance for audio )

5.5.4f1(64bit) please fix!!!!!!!!!!

Still in 5.6.2 f1

Getting it in 5.5.4f1

Still getting this on iOS (fine on Android) using 5.6.2f1.

I'm getting this in Unity 5.6.1f1

This is my code is fine worked in the Unity 5.6.0f3 Personal, OS Win 10

using UnityEngine;
using System.Collections;

public class TestAudio : MonoBehaviour
{
private AudioSource _audiopoint;
private WWW _www;

void Start()
{
_audiopoint = GetComponent<AudioSource>();
}

private void Update()
{
if (Input.GetKeyDown(KeyCode.Space))
{
//StartCoroutine(DownloadAndPlay("http://www.tannerhelland.com/dmusic/AMemoryAway.ogg"));

StartCoroutine(DownloadAndPlay("file:///"+ Application.dataPath + "/UserSounds/" + "/my.ogg"));
}
}

IEnumerator DownloadAndPlay(string url)
{
Debug.Log(url);
_www = new WWW(url);
Debug.Log("Start Dowload");
yield return _www;
Debug.Log("Playing");
_audiopoint = GetComponent<AudioSource>();
_audiopoint.clip = _www.GetAudioClip(false, true, AudioType.OGGVORBIS);
_audiopoint.clip.name = "Downloaded clip";
_audiopoint.Play();
}
}

Still have this in 5.6.0p4
Error: Cannot create FMOD::Sound instance for resource \320A\250, (Operation could not be performed because specified sound/DSP connection is not ready. )
UnityEngine.WWWAudioExtensions:GetAudioClip(WWW, Boolean, Boolean, AudioType)
<DownloadAndSaveAudio>c__Iterator1:MoveNext()
UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr)

[ line 880]
(Filename: Line: 880)

I still have it in unity 5.5.1f1