There is a problem to connect GCP IoT core with BG96

Before, I succeed to connect AWS IoT Core with BG96(LTE module).

And now I'm trying to connect GCP IoT Core with BG96. However, there are some problems.

I followed the guideline of IoT Core and downloaded MQTT server certificates(complete Goolge root CA, RSA key with a self-signed x.509 certificate).

Then, created JWT from jwt.io using another generated RSA key with below header and payload.

After, uploaded key files to cert section of device tab.

At BG96, I set the configurations like below. (root : complete Google root CA, cert : rsa_cert.pem (x.509), key : rsa_private.pem (x.509))

AT+QCDS
+QCDS: "SRV","CAT-M",45012,2500,12BAF1B,R13,3,313,1031,-75,-102,-10,3,128,0,0,0
OK
AT+QSSLCFG="cacert",0,"UFS:root.pem"
OK
AT+QSSLCFG="clientcert",0,"UFS:cert.pem"
OK
AT+QSSLCFG="clientkey",0,"UFS:key.pem"
OK
AT+QSSLCFG="seclevel",0,2
OK
AT+QSSLCFG="sslversion",0,4
OK
AT+QMTCFG="SSL",0,1,0
OK
AT+QMTCFG="will",0,0
OK
AT+QMTCFG="version",0,4
OK
AT+QMTCFG="keepalive",0,60
OK
AT+QMTCFG="session",0,1
OK
AT+QMTOPEN=0,"mqtt.googleapis.com",8883
OK
+QMTOPEN: 0,0
AT+QMTCONN=0,"projects/mqtt-test/locations/asia-east1/registries/test-registry/devices/my-
device","unused",["jwt"](I just covered it up)
OK
+QMTSTAT: 0,1

I don't know why but It keeps disconnecting GCP.

Did I make a mistake somewhere?

I found the problem. The client ID was different. It was mqtt-test-282503, not mqtt-test.