Hello, I am developing a 3D game for our capstone and I am a newbie in using Unity and c#. Can anyone help me with this problem?

I have animation in my buttons and in the Pause Menu, the Resume button animation stops working after used once. but it is still functioning, just the animation stopped. See the video below for ref. and here is the code as well.

    using UnityEngine;
    using UnityEngine.SceneManagement;
    
    public class PauseMenu : MonoBehaviour
    {
        public GameObject pauseMenuUI;
        public static bool isPaused = false;
    
        void Start()
        {
            pauseMenuUI.SetActive(false);
        }
    
        void Update()
        {
            if (Input.GetKeyDown(KeyCode.Escape))
            {
                if (!isPaused)
                {
                    Pause();
                }
                else
                {
                    Resume();
                }
            }
        }
    
        public void Resume()
        {
            pauseMenuUI.SetActive(false);
            Time.timeScale = 1;
            isPaused = false;
            Cursor.lockState = CursorLockMode.Locked;
            Cursor.visible = false;
        }
    
        void Pause()
        {
            pauseMenuUI.SetActive(true);
            Time.timeScale = 0;
            isPaused = true;
            Cursor.lockState = CursorLockMode.None;
            Cursor.visible = true;
        }
        public void MainMenuBtn(int index)
        {
            SceneManager.LoadScene(index);
            Time.timeScale = 1;
            Cursor.visible = true;
        }
    
        public void ExitGame()
        {
            Application.Quit();
        }
    }

Animation Stops Playing