BG96 : AT+QMTSUB => +QMTSTAT: 0,1 error

After AT+QMTCONN succeeds, the following error occurs when executing AT+QMTSUB.
Please tell me what caused it.

[2020-07-09 14:02:25:406_S:] AT+QMTCONN=0,“MyIotThing”
[2020-07-09 14:02:25:458_R:] AT+QMTCONN=0,“MyIotThing”
[2020-07-09 14:02:25:458_R:] OK

[2020-07-09 14:02:25:805_R:] DSR:0 CTS:0 (RI:1) DCD:0

[2020-07-09 14:02:25:854_R:] +QMTCONN: 0,0,0

[2020-07-09 14:02:25:923_R:] DSR:0 CTS:0 (RI:0) DCD:0
[2020-07-09 14:02:29:294_S:] AT+QMTSUB=0,1,"$aws/things/MyIotThing/shadow/update/accepted",1
[2020-07-09 14:02:29:346_R:] AT+QMTSUB=0,1,"$aws/things/MyIotThing/shadow/update/accepted",1
[2020-07-09 14:02:29:346_R:] OK

[2020-07-09 14:02:29:829_R:] +QMTSTAT: 0,1 <==== error

err 1 means Connection is closed or reset by
peer.

pls open and connect server again , thanks