It may be insufficient permission, but how to get permission? the response:

{ "error": { "message": "(#3000) Reading insights of a Page, business, app, domain or event source group not owned by the querying user or application", "type": "OAuthException", "code": 3000, "fbtrace_id": "Anvhbpn1mU-O9kkMWKroqSj" } }