C# CheckBox Checked value cannot change if clicked manually on the form

So I do loop over the form and check "checked" value for all checkboxes. Every time I get "Unchecked" back even if the checkbox is checked on the form.

here is how i loop

   public  class FindAll
{
    public IEnumerable<Control> GetAllChildren(Control root)
    {
        var stack = new Stack<Control>();
        stack.Push(root);

        while (stack.Any())
        {
            var next = stack.Pop();
            foreach (Control child in next.Controls)
                stack.Push(child);
            yield return next;
        }
    }
}

and here how i determine checked state

public List<string> Checked()
    {
        List<string> checkedList = new List<string>();
        var all = new FindAll();
        foreach (var checkbox in all.GetAllChildren(tabPage4).OfType<CheckBox>())
        {
            checkedList.Add(checkbox.CheckState.ToString());
        }
        for (int i = 0; i < 22; i++)
        {
            MessageBox.Show(checkedList.ElementAt(i));
        }
        return checkedList;
    }

no matter if i chech the checkboxes on the form while app is running. i always get "unchecked" value.