How to use Serial1 with XIAO ESP32C3

I want to use Serial1.
At first I used sample code for multi serial,following below.
But, It doesn’t work.(Seral1 Tx : D6 Rx:D7)

Is there any settings or others.

void setup() {
// initialize both serial ports:
Serial.begin(9600);
Serial1.begin(9600);
}

void loop() {
// read from port 1, send to port 0:
if (Serial1.available()) {
int inByte = Serial1.read();
Serial.write(inByte);
}

// read from port 0, send to port 1:
if (Serial.available()) {
int inByte = Serial.read();
Serial1.write(inByte);
}
}

I found the same problem, when i flash this into XIAO ESP32, then the OS can’t recognize the COM. evenif i use another FTD32 USB-COM board and connect to D6/D7, can’t flash program.