Thank you for your answer, it is indeed the case. I customized the random Client_uniqueID, recompiled the libnvds_mqtt_proto.so file, and the problem has been resolved. Thank you once again, and I wish you smooth work ahead!
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_int_distribution<int> dis(0, 100);
int random_number = dis(gen);
string Client_uniqueID = "deepstream" + to_string(random_number);
struct mosquitto* client = mosquitto_new(Client_uniqueID.c_str(), true, NULL);