AWS API Gateway V2 Integration with SQS - CloudFormation - amazon-web-services

Question

I am trying to create a CloudFormation template to deploy an API Gateway HTTP API integrated with SQS. I used the below CF template:
AWSTemplateFormatVersion: "2010-09-09"
Resources:
ExecutionRole:
Type: AWS::IAM::Role
Properties:
RoleName: ExecutionRole
AssumeRolePolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: Allow
Principal:
Service:
- apigateway.amazonaws.com
Action:
- sts:AssumeRole
Path: "/"
Policies:
- PolicyName: root
PolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: Allow
Action:
- sqs:SendMessage
- sqs:ReceiveMessage
- sqs:DeleteMessage
Resource: !Sub "arn:aws:sqs:${AWS::Region}:${AWS::AccountId}:sample-queue"
- Effect: Allow
Action: lambda:InvokeFunction
Resource: "*"
Queue:
Type: AWS::SQS::Queue
Properties:
QueueName: sample-queue
API:
Type: AWS::ApiGatewayV2::Api
Properties:
Body:
openapi: "3.0.1"
info:
title: "HttpApi"
version: "2022-09-29 15:59:08UTC"
paths:
/:
post:
responses:
default:
description: "Default response for POST /"
x-amazon-apigateway-integration:
integrationSubtype: "SQS-SendMessage"
credentials: !Sub "arn:aws:iam::${AWS::AccountId}:role/ExecutionRole"
requestParameters:
MessageBody: "$request.body"
QueueUrl: !Sub "https://sqs.${AWS::Region}.amazonaws.com/${AWS::AccountId}/sample-queue"
payloadFormatVersion: "1.0"
type: "aws_proxy"
connectionType: "INTERNET"
timeoutInMillis: 30000
x-amazon-apigateway-importexport-version: "1.0"
Stage:
Type: AWS::ApiGatewayV2::Stage
Properties:
StageName: v1
ApiId: !Ref API
Deployment:
Type: AWS::ApiGatewayV2::Deployment
Properties:
ApiId: !Ref API
StageName: !Ref Stage
The API this generates looks good in the web console, but not sure why, any POST to this API gives an error:
{
"message": "Not Found"
}
Perhaps I am missing something very silly. But not able to locate it. Can you please help me identify?