Deploy angular app on Digitalocean App Platform

it’s my first time deploying an Angular application on DigitalOcean app platform (I develop React application usually). The problem I am experiencing here is the failure of application’s health checks during the deployment phase. I read the DigitalOcean’s documentation about health checks but still i can’t figure out what’s the problem.

These are my App Spec file and the screenshots of the DO log console.

alerts:
- rule: DEPLOYMENT_FAILED
- rule: DOMAIN_FAILED
envs:
- key: NODE_OPTIONS
  scope: RUN_AND_BUILD_TIME
  value: max-old-space-size=4096
- key: GENERATE_SOURCEMAP
  scope: RUN_AND_BUILD_TIME
  value: "false"
ingress:
  rules:
  - component:
      name: ------------
    match:
      path:
        prefix: /
name: seahorse-app
region: fra
services:
- build_command: npm run build
  environment_slug: node-js
  github:
    branch: master
    deploy_on_push: true
    repo: -----------------
  health_check:
    http_path: /
  http_port: 4200
  instance_count: 1
  instance_size_slug: professional-s
  name: ------------
  run_command: npm start
  source_dir: /