Resolved Problem when trying to replace TextMeshPro text with code

When the code is loaded the variable disappears and this error appears:

NullReferenceException: Object reference not set to an instance of an object

LoadingPanelExtern.ChangeUsernameText () (at Assets/Jachi/Scripts/LoadingPanelExtern.cs:56)

LoadingPanelExtern.Update () (at Assets/Jachi/Scripts/LoadingPanelExtern.cs:40)

This is my code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using TMPro;
5. using PlayFab;
6. using PlayFab.ClientModels;
7.  
8. public class LoadingPanelExtern : MonoBehaviour
9. {
10.  
11.     [Header("Importante")]
12.     public GameObject LoadingPanelExtern2;
13.     public GameObject AccountsPanel;
14.     public GameObject UI1;
15.     public GameObject UI2;
16.     public GameObject UI3;
17.     public float targetTime = 6.0f;
18.  
19.     [Header("Interfaz")]
20.     public TextMeshProUGUI UsernameTextHome;
21.     //public TextMeshProUGUI UsernameTextSettings;
22.     public TextMeshProUGUI UsernameTextRadio;
23.  
24.     //string PFUA = GetComponent<PlayFabManager>().PlayFabUserActual;
25.  
26.     void Start()
27.     {
28.         AccountsPanel.SetActive(false);
29.         UI1.SetActive(true);
30.         UI2.SetActive(true);
31.         UI3.SetActive(true);
32.     }
33.     void Update()
34.     {
35.         targetTime -= Time.deltaTime;
36.  
37.         if (targetTime <= 0.0f)
38.         {
39.             timerEnded();
40.             ChangeUsernameText();
41.         }
42.  
43.     }
44.  
45.     void timerEnded()
46.     {
47.         LoadingPanelExtern2.SetActive(false);
48.     }
49.  
50.     void ChangeUsernameText()
51.     {
52.         UsernameTextHome = GetComponent<TextMeshProUGUI>();
53.         UsernameTextRadio = GetComponent<TextMeshProUGUI>();
54.         //UsernameTextSettings = GetComponent<TextMeshProUGUI>();
55.  
56.         UsernameTextHome.text = PlayerPrefs.GetString("username");
57.         UsernameTextRadio.text = PlayerPrefs.GetString("username");
58.     }
59. }
60.  

VIDEO:

 

thanks, it worked