부트스트랩을 통해 모달을 추가한 후, 버튼을 클릭해도 모달이 나타나지 않는 경우 다음과 같이 시도해보세요.
<head>
<head>
<!-- Bootstrap CSS 존재 확인-->
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0-alpha3/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-KK94CHFLLe+nY2dmCWGMq91rCGa5gtU4mk92HdvYe+M/SXH301p5ILy+dN9+nJOZ" crossorigin="anonymous">
<!-- ... -->
</head>
<body>
<!-- ... -->
<!-- Bootstrap Popper 존재 확인 -->
<script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.11.7/dist/umd/popper.min.js" integrity="sha384-zYPOMqeu1DAVkHiLqWBUTcbYfZ8osu1Nd6Z89ify25QV9guujx43ITvfi12/QExE" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0-alpha3/dist/js/bootstrap.min.js" integrity="sha384-Y4oOpwW3duJdCWv5ly8SCFYWqFDsfob/3GkgExXKV4idmbt98QcxXYs9UoXAB7BZ" crossorigin="anonymous"></script></body>
해당 코드를 추가하면 모달이 정상적으로 보이게 됩니다