Why does the Ansible Automation Platform 2.5 installer fail at the task “Ensure automation gateway is ready” with the status code 503 error?

Issue

• AAP 2.5 installer fails at the task Ensure automation gateway is ready with the status code 503 error.

  2025-07-23 17:56:08,066 p=1528 u=example n=ansible | TASK [ansible.containerized_installer.automationgateway : Ensure automation gateway is ready] ***********************
  2025-07-23 18:12:42,296 p=1528 u=example n=ansible | fatal: [gateway.example.com]: FAILED! => {"attempts": 30, "changed": false, "connection": "close", "content_length": "66", "content_type": "application/octet-stream", "date": "Wed, 23 Jul 2025 09:12:42 GMT", "elapsed": 21, "msg": "Status code was 503 and not [200]: HTTP Error 503: Service Temporarily Unavailable", "redirected": false, "server": "nginx", "status": 503, "url": "https://gateway.example.com:8446/api/gateway/v1/ping/"}