Ok i was asking because it said this on the Facebook developers website: "As of April 4, 2018, this node and its edges return empty data sets for GET operations unless the calling app has gone through App Review. Please see the Groups API section of the Breaking Changes changelog for more information."
1) Development Mode — Apps in development mode are now rate-limited to 200 calls per hour, per page-app pair, and can only access Users who have a role on the app (admin, developer, or tester).
2) Public Mode — Apps in public mode no longer allow their admins, developers, or testers to access permissions or features that normally require app review. This affects all apps built after May 1st, 2018, immediately. Apps built before then will not be affected until August 1st, 2018.