Can't load scene or do any event in unity after firebase auth task completed

Question

Problem shortcut: unity ui doesn't respond to code after I logged in with firebaseAuth.

The question is: how can I make changes to unity ui after I connected to firebaseAuth ?

Problem details: i have made a firebase auth system and it works fine and all massages was printed fine in system.print() but when i need to desplay the Auth error in UI.text its not working even after the login in success and i want to change scene to make player enter the game it the SceneManager.loadscene() didnt work..

this is my code:

using UnityEngine;
using UnityEngine.UI;
using Firebase.Auth;

public class AccountsManager : MonoBehaviour
{
    public void Login()
    {
        if (Email.text == "" && Password.text == "")
        {
            LoginMassageText.text = "Enter Email and Password";
        }
        else if (Email.text == "")
        {
            LoginMassageText.text = "Enter Email";
        }
        else if (Password.text == "")
        {
            LoginMassageText.text = "Enter Password";
        }
        else   
        {
            FirebaseAuth.DefaultInstance.SignInWithEmailAndPasswordAsync(Email.text, Password.text).ContinueWith((task =>
            {
                if (task.IsCanceled)
                {
                    Firebase.FirebaseException e = task.Exception.Flatten().InnerExceptions[0] as Firebase.FirebaseException;
                    ErroeHundler((AuthError)e.ErrorCode);
                    Debug.Log("1" + e);
                    return;
                }
                else if (task.IsFaulted)
                {                        
                    Firebase.FirebaseException e = task.Exception.Flatten().InnerExceptions[0] as Firebase.FirebaseException;
                    ErroeHundler((AuthError)e.ErrorCode);
                    return;
                }
                else if (task.IsCompleted)
                {
                    Debug.Log("login successful");
                    return;
                }
            }));        
        }      
    }

    void ErroeHundler(AuthError Error)
    {       
        print(Error.ToString());
        LoginMassageText.text = "Invalid Email"; //this not working

        switch(Error)
        {
            case AuthError.InvalidEmail:
                LoginMassageText.text = "Invalid Email"; //this not working
                print("invild");
            break;

            case AuthError.MissingEmail:
                LoginMassageText.text = "Invalid Email"; //this not working
                print("missingemail");
                break;

            default:
            LoginMassageText.text = "Invalid Email"; //this not working
            break;
        }
    }