The API returns 503 that means Unavailable.
https://ja.developer.box.com/guides/api-calls/permissions-and-errors/common-errors/
https://ja.developer.box.com/guides/api-calls/permissions-and-errors/common-errors/
503 response json is the following.
{"type": "error", "status": 503, "code": "service_unavailable", "help_url": "http://developers.box.com/docs/#errors", "message": "Service Unavailable", "request_id": "13cba857cea46336418315c0aa8e2b484"}
{"type": "error", "status": 503, "code": "service_unavailable", "help_url": "http://developers.box.com/docs/#errors", "message": "Service Unavailable", "request_id": "13cba857cea46336418315c0aa8e2b484"}