Meta requires every app that reads or sends Instagram messages to pass App Review before it can be used by accounts the developer does not own. Until that review completes, connecting an account issues a token that looks valid but returns nothing on every graph.instagram.com call — which is why a connection can appear to succeed and still deliver zero messages.

This applies to every product in this category, not something specific here. Testers added to the Meta app can use Instagram today; everyone else should lead with WhatsApp or Messenger, both fully live, while review is pending.

See the full, live breakdown at Help → Channel status.