Button goes null when trying to access it - unity3d

Question

As the title suggests, my button (closeImage) goes null when I try to access it.
I have a canvas that pops up an image based on a tapped marker (button component) on a map. The said canvas will show the image together with the button in question. Clicking on the button closes the pop-up;
The button in question
However, once I press on the marker on the map to show the pop-up image, it gives me an error that the Close image is null. The close button does show on the first time I press on the marker on the map and able to close the pop-up, even with the error message. But once I click on the same marker on the map again, the image shows but the close button is not showing anymore.
Here's my block of code:
public class TappedMarkerManager : MonoBehaviour {
private static TappedMarkerManager instance;
private List<GameObject> markerImageList = new List<GameObject>();
string tappedMarkerName;
Button closeImage;
GameObject closeImageGO;
public static TappedMarkerManager Instance {
get {
if (instance == null) {
instance = FindObjectOfType<TappedMarkerManager>();
}
return instance;
}
}
void Start() {
closeImageGO = GameObject.FindGameObjectWithTag("close_img");
if(closeImageGO != null) {
closeImage = closeImageGO.GetComponent<Button>();
closeImage.onClick.AddListener(TappedMarkerInformation);
} else {
Debug.Log("closeImageGO is null");
}
//Loop through preview images.
//This will dynamically add the images on the list if more markers will be added on the map
//Use tag "marker_img"; must be same name with the marker and image
var markerImages = GameObject.FindGameObjectsWithTag("marker_img");
foreach(var markerImage in markerImages) {
TappedMarkerManager.Instance.markerImageList.Add(markerImage.gameObject);
//Set false to hide it at first
markerImage.SetActive(false);
}
}
public void TappedMarkerInformation() {
var name = tappedMarkerName;
foreach(var img in TappedMarkerManager.Instance.markerImageList) {
if(name == img.GetComponent<Image>().name) {
img.SetActive(true);
if(closeImage != null) {
if(!closeImage.gameObject.activeInHierarchy) {
closeImage.gameObject.SetActive(true);
}
} else {
Debug.LogError("Close image is null");
}
}
if(GetButtonName() == "ExitBtn") {
img.SetActive(false);
closeImage.gameObject.SetActive(false);
}
}
}
public void SetTappedName(string name) {
tappedMarkerName = name;
TappedMarkerInformation();
}
//Get the name of the button pressed
public string GetButtonName() {
if(EventSystem.current.currentSelectedGameObject != null) {
string ClickedButtonName = EventSystem.current.currentSelectedGameObject.name;
return ClickedButtonName;
} else {
return "";
}
}
}
The markers on the map are controlled from another script with:
...
TappedMarkerManager tappedMarkerManager;
tappedMarkerManager = new TappedMarkerManager();
...
private void HandleFingerTap(LeanFinger finger) {
Ray ray = Camera.main.ScreenPointToRay(finger.ScreenPosition);
if (Physics.Raycast(ray, out RaycastHit hit)) {
string markerName = hit.collider.gameObject.name;
tappedMarkerManager.SetTappedName(markerName);
}
}
Any help is highly appreciated. Thank you. I can provide the github repository if needed.
What I tried so far:
I already tried setting up the closeImage in the Inspector with the button
Made sure that the GameObject has the button component
Checked and verified on the hierarchy that the closeImage button is not being destroyed