我查参考文档中，通过命令通过MCU发送命令给模组，
但是一直无法连接到EMQX的Broker，以下是我的跟模块的收发日志
I (19843) modem: APN configured successfully
I (19843) modem: Activating PDP context...
I (19844) modem: Sent: AT+CREG?
I (24850) modem: Received:
+CREG: 0,5
OK
I (24850) modem: Network registered (roaming) after 1 attempts
I (24851) modem: Sent: AT+CGACT=1,1
I (24956) modem: Received:
OK
I (24956) modem: PDP context activated
I (24957) modem: Sent: AT+QMTCFG="recv/mode",0,0,1
I (25064) modem: Received:
OK
I (25064) modem: Sent: AT+QMTCFG="SSL",0,1,2
I (25171) modem: Received:
OK
I (28408) modem: Sent: AT+QSSLCFG="cacert",2,"UFS:ca.pem"
I (28516) modem: Received:
OK
I (28516) modem: Sent: AT+QSSLCFG="seclevel",2,1
I (28623) modem: Received:
OK
I (28623) modem: Sent: AT+QSSLCFG="sslversion",2,4
I (28730) modem: Received:
OK
I (28730) modem: Sent: AT+QSSLCFG="ciphersuite",2,0xFFFF
I (28838) modem: Received:
OK
I (28839) modem: Sent: AT+QSSLCFG="ignorelocaltime",2,1
I (28946) modem: Received:
OK
I (28947) modem: Sent: AT+QMTOPEN=0,"broker.emqx.io",8883
I (89002) modem: Received:
OK
I (89004) modem: Sent: AT+QMTCONN=0,"aaaaaaaaaaaaaaa","bbbbbbbbbbbbbbbbbbbbbbbb","ccccccccccccccccc"
I (104016) modem: Received:
ERROR
E (104017) modem: Failed to connect to MQTT broker
我从broker.emqx.io 下载的CA文件，然后将CA证书传给了模组保存起来。
我不太明白为什么发送了
AT+QMTOPEN=0,"broker.emqx.io",8883
命令后，等待了60s的时间，模块只返回了OK,但并没有返回+QMTOPEN: 0,0
对比了文档，我没有找出问题出在哪