Что не так в коде? (VK API)

{"error":{"error_code":917,"error_msg":"You don't have access to this chat","request_params":[{"key":"v","value":"5.103"},{"key":"chat_id","value":"53"},{"key":"group_id","value":"199904779"},{"key":"random_id","value":"548945184"},{"key":"method","value":"messages.send"},{"key":"oauth","value":"1"}]}}

Что я не так сделал?