question

Many thanks for your input, I can pass an instance of MonoBehaviour into the login method but I am not sure how to pass that onto the other methods if they are successful

So

Login is called as below

 void Awake ()


    {
        PlayFabHelpers.Login(this);    
    }

and the new Playfab helper code is as below. I can't work out how to pass justToStartCoroutine to OnLoginSuccess then onto OnSucess then onto DownloadFile . . .

using PlayFab;
using PlayFab.ClientModels;
using System;
using System.Collections;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;


public class PlayFabHelpers: MonoBehaviour
{
        


    public static void Login(MonoBehaviour justToStartCoroutine)
    {
        if (string.IsNullOrEmpty(PlayFabSettings.staticSettings.TitleId))
        {
              PlayFabSettings.staticSettings.TitleId = "FE59A";
        }
        var request = new LoginWithCustomIDRequest { CustomId = "TestGuy", CreateAccount = true };
        PlayFabClientAPI.LoginWithCustomID(request, OnLoginSuccess, OnLoginFailure);
               
    }


    private static void OnLoginSuccess(LoginResult result)
    {
        GetDownloadUrl("Levels.json", OnSuccess);
    }


    private static void OnLoginFailure(PlayFabError error)
    {
        Debug.LogWarning("Something went wrong with your first API call.  :(");
        Debug.LogError("Here's some debug information:");
        Debug.LogError(error.GenerateErrorReport());
    }


    private static void OnSuccess(string obj)
    {
        DownloadFile(obj);
    }


    public static void AuthenticateWithPlayFab()
    {
        Debug.Log("Logging into PlayFab...");
        LoginWithCustomIDRequest request = new LoginWithCustomIDRequest() { TitleId = PlayFabSettings.staticSettings.TitleId, CustomId = SystemInfo.deviceUniqueIdentifier, CreateAccount = true };
        PlayFabClientAPI.LoginWithCustomID(request, OnLoginSuccess, OnLoginFailure, null);
    }


    public static void DownloadFileFromCDN(string key)
    {
        GetDownloadUrl(key, presignedUrl =>
        {
            Console.WriteLine("");
        });
    }


    static void GetDownloadUrl(string key, Action<string> onComplete)
    {
        PlayFabClientAPI.GetContentDownloadUrl(new GetContentDownloadUrlRequest()
        {
            Key = key,
            ThruCDN = true
        }, result => onComplete(result.URL),
        error => Debug.LogError(error.GenerateErrorReport()));
    }


    private static IEnumerator DownloadFile(string thePath)
    {
        var uwr = new UnityWebRequest(thePath, UnityWebRequest.kHttpVerbGET);
        string path = Path.Combine(Application.persistentDataPath, "Levels.json");
        uwr.downloadHandler = new DownloadHandlerFile(path);
        yield return uwr.SendWebRequest();
        if (uwr.isNetworkError || uwr.isHttpError)
            Debug.LogError(uwr.error);
        else
            Debug.Log("File successfully downloaded and saved to " + path);
    }
}

using PlayFab;
using PlayFab.ClientModels;
using System;
using System.Collections;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;
 
 
public static class PlayFabHelpers
{
     static public MonoBehaviour  instance; 

    public static void Login(MonoBehaviour justToStartCoroutine)
    {
        instance = justToStartCoroutine;

        if (string.IsNullOrEmpty(PlayFabSettings.staticSettings.TitleId))
        {
              PlayFabSettings.staticSettings.TitleId = "blablabla";
        }
        var request = new LoginWithCustomIDRequest { CustomId = "TestGuy", CreateAccount = true };
        PlayFabClientAPI.LoginWithCustomID(request, OnLoginSuccess, OnLoginFailure);
               
    }
 
 
    private static void OnLoginSuccess(LoginResult result)
    {
        GetDownloadUrl("Levels.json", OnSuccess);
    }
 
 
    private static void OnLoginFailure(PlayFabError error)
    {
        Debug.LogWarning("Something went wrong with your first API call.  :(");
        Debug.LogError("Here's some debug information:");
        Debug.LogError(error.GenerateErrorReport());
    }
 
 
    private static void OnSuccess(string obj)
    {
        instance.StartCoroutine(DownloadFile(obj));
    }
 
 
    public static void AuthenticateWithPlayFab()
    {
        Debug.Log("Logging into PlayFab...");
        LoginWithCustomIDRequest request = new LoginWithCustomIDRequest() { TitleId = PlayFabSettings.staticSettings.TitleId, CustomId = SystemInfo.deviceUniqueIdentifier, CreateAccount = true };
        PlayFabClientAPI.LoginWithCustomID(request, OnLoginSuccess, OnLoginFailure, null);
    }
 
 
    public static void DownloadFileFromCDN(string key)
    {
        GetDownloadUrl(key, presignedUrl =>
        {
            Console.WriteLine("");
        });
    }
 
 
    static void GetDownloadUrl(string key, Action<string> onComplete)
    {
        PlayFabClientAPI.GetContentDownloadUrl(new GetContentDownloadUrlRequest()
        {
            Key = key,
            ThruCDN = true
        }, result => onComplete(result.URL),
        error => Debug.LogError(error.GenerateErrorReport()));
    }
 
 
    private static IEnumerator DownloadFile(string thePath)
    {
        var uwr = new UnityWebRequest(thePath, UnityWebRequest.kHttpVerbGET);
        string path = Path.Combine(Application.persistentDataPath, "Levels.json");
        uwr.downloadHandler = new DownloadHandlerFile(path);
        yield return uwr.SendWebRequest();
        if (uwr.isNetworkError || uwr.isHttpError)
            Debug.LogError(uwr.error);
        else
            Debug.Log("File successfully downloaded and saved to " + path);
    }
}

This code show how to pass the MonoBehaviour instance, it may be helpful for you.

Working now , thanks very much for your help