Google Cloud Platform - API Gateway Cannot PUT/DELETE Error - google-cloud-platform

Question

I'm struggling to pass the path params from my gateway to the actual endpoints and I use PUT method to do the update and DELETE method to do a delete action in API which is built with Google Cloud Functions.
Here is my API Gateway Config:
# openapi2-functions.yaml
swagger: '2.0'
info:
title: cpd-api
description: API Gateway Config
version: 1.0.0
schemes:
- https
produces:
- application/json
paths:
/users/{user_id}:
put:
summary: Update an existing user
operationId: update-user-cpd
parameters:
- name: user_id
in: path
description: User ID to be updated
required: true
type: string
x-google-backend:
address: https://asia-southeast2-project-id.cloudfunctions.net/cpd_user
path_translation: APPEND_PATH_TO_ADDRESS
responses:
'200':
description: User updated successfully
schema:
type: object
delete:
summary: Delete an existing user
operationId: delete-user-cpd
parameters:
- name: user_id
in: path
description: User ID to be deleted
required: true
type: string
x-google-backend:
address: https://asia-southeast2-project-id.cloudfunctions.net/cpd_user
path_translation: APPEND_PATH_TO_ADDRESS
responses:
'200':
description: User deleted successfully
schema:
type: object
/users:
get:
summary: Get Users data
operationId: get-users-cpd
x-google-backend:
address: https://asia-southeast2-project-id.cloudfunctions.net/cpd_user
responses:
'200':
description: User retrieved successfully
schema:
type: object
post:
summary: Create a new user
operationId: create-user-cpd
x-google-backend:
address: https://asia-southeast2-project-id.cloudfunctions.net/cpd_user
responses:
'200':
description: User created successfully
schema:
type: object
If I call the Functions URL directly with PUT/DELETE method it's working as expected.
e.g. PUT https://asia-southeast2-project-id.cloudfunctions.net/cpd_user/1
But, when I try to call it by using the API Gateway URL it gives me below errors with 404 HTTP Status:
Cannot PUT /users/1
Cannot DELETE /users/1
Here is the cpd_user index.js file.
I use express JS to define the routes
const _utils = require('./utils');
const _controller = require('./controllers');
const express = require('express');
const app = express();
const UserController = new _controller.UserController();
app.get('/', _utils.jwtFilter, UserController.getUserAction);
app.post('/', UserController.createUserAction);
app.delete('/{user_id}', _utils.jwtFilter, UserController.deleteUserAction);
app.put('/{user_id}', _utils.jwtFilter, UserController.updateUserAction);
exports.cpdUser = app;
I have checked the log but I didn't get any useful info there.
Please help me to fix this issue.
Thanks.