Crud app API POST error, not able to find the issue - node.js

Question

Making a crud app with Node and Mongo.
While updating a user the API is not able to POST the data and returning an error in the browser Cannot POST /update-user
I am able to add a user, but while updating the user it is returning an error.
This is my Add user page:
<!-- include header -->
<%- include('include/_header') %>
<!-- /include header -->
<!--Main site-->
<main id="site-main">
<div class="container">
<div class="box-nav d-flex justify-between">
<div class="filter">
<i class='fas fa-angle-double-left'></i>All Users
</div>
</div>
<div class="form-title text-center">
<h2 class='text-dark'>New User</h2>
<span class='text-light'>Use the form below to create a new account</span>
</div>
<!-- add user form -->
<%- include('include/_form') %>
</div>
</main>
<!--Main site-->
<!-- include footer -->
<%- include('include/_footer') %>
<!-- /include footer -->
This is the footer:
<script src="<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js" integrity="sha512-894YE6QWD5I59HgZOGReFYm4dnWc1Qt5NtvYSaNcOP+u1T9qYdvdihz0PPSiiqn/+/3e7Jo4EaG7TubfWGUrMQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
<script src="../../assets/js/index.js"></script>
</body>
</html>
This is the Index.js connected to the footerL:
$("#add_user").submit(function(event){
alert("Data inserted successfully");
})
$("#update_user").submit(function(event){
event.preventDefault();
var unindexed_array = $(this).serializeArray();
var data = {}
$.map(unindexed_array, function(n, i){
data[n['name']] = n['value']
})
})
This is the index.js connected to the footer:
$("#add_user").submit(function(event){
alert("Data inserted successfully");
})
$("#update_user").submit(function(event){
event.preventDefault();
var unindexed_array = $(this).serializeArray();
var data = {}
$.map(unindexed_array, function(n, i){
data[n['name']] = n['value']
})
})
This is the Update user form:
<!-- include header -->
<%- include('include/_header') %>
<!-- /include header -->
<!-- Main Site -->
<main id="site-main">
<div class="container">
<div class="box-nav d-flex justify-between">
<div class="filter">
<i class="fas fa-angle-double-left"></i> All Users
</div>
</div>
<div class="form-title text-center">
<h2 class="text-dark">Update User</h2>
<span class="text-light">Use the below form to Update an account</span>
</div>
<!-- add user form -->
<!-- form handling -->
<form method="POST" id="update_user">
<div class="new_user">
<div class="form-group">
<label for="name" class="text-light">Name</label>
<input type="hidden" name="id" value="<%= user._id %>">
<input type="text" name="name" value="<%= user.name %>" placeholder="Mark Stoenis">
</div>
<div class="form-group">
<label for="Email" class="text-light">Email</label>
<input type="text" name="email" value="<%= user.email%>" placeholder="example#gmail.com">
</div>
<div class="form-group">
<label for="gender" class="text-light">Gender</label>
<div class="radio inline">
<input type="radio" id="radio-2" name="gender" value="Male" <%= user.gender == 'Male' ? 'checked' : '' %>>
<label for="radio-2" class="radio-label">Male</label>
</div>
<div class="radio inline">
<input type="radio" id="radio-3" name="gender" value="Female" <%= user.gender == 'Female' ? 'checked' : '' %> >
<label for="radio-3" class="radio-label">Female</label>
</div>
</div>
<div class="form-group">
<label for="gender" class="text-light">Status</label>
<div class="radio inline">
<input type="radio" id="radio-4" name="status" value="Active" <%= user.status == 'Active' ? 'checked' : '' %> >
<label for="radio-4" class="radio-label">Active</label>
</div>
<div class="radio inline">
<input type="radio" id="radio-5" name="status" value="Inactive" <%= user.status == 'Inactive' ? 'checked' : '' %> >
<label for="radio-5" class="radio-label">Inactive</label>
</div>
</div>
<div class="form-group">
<button type="submit" class="btn text-dark update">Save</button>
</div>
</div>
</form>
</div>
</main>
<!-- /Main Site -->
<!-- include footer -->
<%- include('include/_footer') %>
<!-- /include footer -->