HFP AG无法建立音频连接的原因？

使用官方例程：hfp_ag，IDF版本是4.2.3，能够与远端设备建立蓝牙连接，但是无法建立音频连接，输出日志如下：
Connect Audio
[0;33mW (42785) BT_BTM: BTM Remote does not support 3-EDR eSCO
[0;31mE (42785) BT_BTM: btm_sco_connected, handle 81
[0;33mW (42785) BT_BTM: BTM Remote does not support 3-EDR eSCO
[0;32mI (42795) BT_APP_HF: APP HFP event: AUDIO_STATE_EVT
[0;31mE (42795) BT_BTM: btm_sco_connected, handle 81
[0;32mI (42805) BT_APP_HF: --Audio State connecting
[0;32mI (42805) BT_APP_HF: APP HFP event: AUDIO_STATE_EVT
[0;32mI (42815) BT_APP_HF: --Audio State disconnected
[0;33mW (98925) BT_RFCOMM: port_rfc_closed RFCOMM connection in server:1 state 2 closed: Peer connection failed (res: 16)
[0;32mI (98925) BT_APP_HF: APP HFP event: CONNECTION_STATE_EVT
[0;32mI (98935) BT_APP_HF: --connection state DISCONNECTED, peer feats 0x0, chld_feats 0x0
[0;33mW (100565) BT_APPL: new conn_srvc id:5, app_id:0
[0;32mI (100575) BT_APP_HF: APP HFP event: CONNECTION_STATE_EVT
[0;32mI (100585) BT_APP_HF: --connection state CONNECTED, peer feats 0x0, chld_feats 0x0
[0;31mE (100805) BT_BTM: tBTM_SEC_DEV:0x3ffc1c88 rs_disc_pending=0