In app update throwing error "user cancelled" when i click on update button in update prompt

I am trying to implement in app update in my unity game.

For testing, I just implement flexible update and create new release in internal testing track and upload one more version with higher version code.

When I test it, the flexible update prompt is showing correctly, but when click on update, it is throwing ErrorUserCancelled.

Here is my in app update manager. I have written code after reading Google doc, but there are lot of things unclear, so I used chat gpt but still something is wrong.

Here is error I get in logcat:

My code:

using System.Collections;
using UnityEngine;
using Google.Play.AppUpdate;
using Google.Play.Common;
using UnityEngine.UI;

public class InAppUpdate : MonoBehaviour
{
    private AppUpdateManager appUpdateManager;

    // The result from checking for an update, contains information about available updates.
    private AppUpdateInfo appUpdateInfoResult;

    void Start()
    {
        // Initialize the AppUpdateManager.
        appUpdateManager = new AppUpdateManager();

        // Start checking for updates immediately.
        StartCoroutine(CheckForUpdate());
    }

    IEnumerator CheckForUpdate()
    {
        // Creates a PlayAsyncOperation to check for update info.
        PlayAsyncOperation<AppUpdateInfo, AppUpdateErrorCode> appUpdateInfoOperation =
            appUpdateManager.GetAppUpdateInfo();

        // Wait until the operation is done.
        yield return appUpdateInfoOperation;

        // If the operation encounters an error, log it and return.
        if (appUpdateInfoOperation.Error != AppUpdateErrorCode.NoError)
        {
            Debug.LogError("Error checking for update: " + appUpdateInfoOperation.Error);
            yield break;
        }

        // Get the AppUpdateInfo result.
        appUpdateInfoResult = appUpdateInfoOperation.GetResult();

        // Check if an update is available and if a flexible update is allowed.
        if (appUpdateInfoResult.UpdateAvailability == UpdateAvailability.UpdateAvailable)
        {
            if (appUpdateInfoResult.IsUpdateTypeAllowed(AppUpdateOptions.ImmediateAppUpdateOptions()))
            {
                StartCoroutine(StartFlexibleUpdate());
            }
        }
        else
        {
            Debug.LogError("Update is not available");
        }
    }

    IEnumerator StartFlexibleUpdate()
    {
        // Define app update options for a flexible update.
        var appUpdateOptions = AppUpdateOptions.FlexibleAppUpdateOptions();

        // Creates an AppUpdateRequest to monitor the update flow.
        var startUpdateRequest = appUpdateManager.StartUpdate(appUpdateInfoResult, appUpdateOptions);

        // Loop while the update is not yet done.
        while (!startUpdateRequest.IsDone)
        {
            // For flexible flow, the user can continue to use the app while
            // the update downloads in the background.
            // No UI elements here, as requested.
            yield return null;
        }

        // Once IsDone, check for errors from the StartUpdate operation.
        if (startUpdateRequest.Error != AppUpdateErrorCode.NoError)
        {
            Debug.LogError("Error starting flexible update: " + startUpdateRequest.Error);
            yield break;
        }

        // After the StartUpdate operation is done, re-fetch AppUpdateInfo to get the latest InstallStatus.
        var updatedAppUpdateInfoOperation = appUpdateManager.GetAppUpdateInfo();
        yield return updatedAppUpdateInfoOperation;

        if (updatedAppUpdateInfoOperation.Error != AppUpdateErrorCode.NoError)
        {
            Debug.LogError("Error re-fetching update info after download: " + updatedAppUpdateInfoOperation.Error);
            yield break;
        }

        AppUpdateInfo updatedAppUpdateInfo = updatedAppUpdateInfoOperation.GetResult();

        // Check if the download completed successfully using the updated InstallStatus.
        if (updatedAppUpdateInfo.AppUpdateStatus == AppUpdateStatus.Downloaded)
        {
            // Downloaded successfully, proceed to complete the update.
            StartCoroutine(CompleteFlexibleUpdate());
        }
        else
        {
            // Handle other download statuses if necessary (e.g., pending, failed).
            // This might occur if the download didn't complete for some reason even after IsDone.
            Debug.LogWarning("Flexible update install status after download: " + updatedAppUpdateInfo.AppUpdateStatus);
        }
    }

    IEnumerator CompleteFlexibleUpdate()
    {
        // Request the app update to be installed.
        var result = appUpdateManager.CompleteUpdate();
        yield return result;

        // This line should typically not be reached if the update is successful,
        // as the app will restart. If it is reached, an error occurred.
        if (result.Error != AppUpdateErrorCode.NoError)
        {
            Debug.LogError("Error completing flexible update: " + result.Error);
        }
    }
}

I follow all things uploading on testing tracks and increment version code. My device is already in testing emails.

I downloaded older version from internal testing link and then I upload new version.

I am getting prompt correctly, but update button not start updating instead throwing error user cancelled, something is wrong in my implementation maybe.

The thing is I uploaded 20+ version again in testing tracks because I get a "class missing" error, but somehow fixed it by adding in main template.

At this time, I am very frustrated by uploading new versions again and again.