arduino due and silvermate bluetooth serial

Hardware Arduino Due
#1

this is my code:

void setup() {
        Serial.begin(9600);
        pinMode(50,OUTPUT);
         digitalWrite(50,LOW);
}

void loop() {

     
        if (Serial.available() > 0) {
                
             char SerialChar= Serial.read();
             if(SerialChar=='H'){digitalWrite(50,HIGH);}
             if(SerialChar=='L'){digitalWrite(50,LOW);}
             Serial.println(SerialChar);
        }
}

I can connect, I can pair the devices, but not to send and receive data.why?

I tried to use blue serial for Android, but I can not turn the LED on.
Thanks

#2