Subscribed to market_trades for BTC-PERP-INTX, but no messages received

URL:wss://advanced-trade-ws.coinbase.com

send:{“product_ids”:[“BTC-PERP-INTX”],“api_key”:“api_key”,“signature”:“signature”,“channel”:“market_trades”,“type”:“subscribe”,“timestamp”:“1701238349”}
received :{“channel”:“subscriptions”,“client_id”:“”,“timestamp”:“2023-11-29T06:12:30.923346749Z”,“sequence_num”:0,“events”:[{“subscriptions”:{}}]}