Why post method does not work in blogger?

Question

I have blogger website. I am making a contact form by editing HTML. But the post method doesn't work when I submit the form. It shows error "Method Not Allowed Error 405".

Can anyone help me please?

<form name="google-sheet" method="post">
<h1>Registration</h1><br>

Your Name: <input type="text" name="name" required><br>
Your message: <input type="text" name="msg" required><br>

<br><br>
<button type="submit">Submit</button>
</form>
          <script>
            const scriptURL = 'https://script.google.com/macros/s/AKfycbzKqduyPdrNj2XMNKah5T2VJ92IFIRYkQx3w5uXazMc9ZSXCFCh/exec'
            const form = document.forms['google-sheet']
          
            form.addEventListener('submit', e => {
              e.preventDefault()
              fetch(scriptURL, { method: 'POST', body: new FormData(form)})
                .then(response => alert("Your response has been  recorded!"))
                .catch(error => console.error('Error!', error.message))
            })
          </script>

        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
</body>
</html>