Sending AT commands to USR ethernet module.

Hi guys:
I have my arduino uno connected to usr-tcp232-t2 via serial interface.
Project works ok , I can send and receive data over the network.
Now , I would like to read ethernet module mac address during setup loop.
Documentation says it is possible to read mac address using AT commands.
After contanting vendor support , explained how to do it but did not provide any working example.
I need to send the "+++a" string , then the "AT+MAC" command , followed by "\r\n"
This is what im doing:

String str1 = "";
String str2 = "";

void setup(){
   Serial.begin(9600);
   str1.reserve(200);
   str2.reserve(200);

    delay(2000);
    Serial.println("+++");

    while(Serial.available() > 0 ){
     str1 = Serial.readString();
    }

    Serial.println("a");

    while(Serial.available() > 0 ){
     str1 = Serial.readString();
    }
    
    Serial.println("AT+MAC\r\n");

    while(Serial.available() > 0 ){
     str2 = Serial.readString();
    }
 
}
 
void loop() {
Serial.print("data from AT:");
Serial.println(str2);
delay(1000);    
}

Well ... this is not working.
btw:
Baud rate is ok , I strings are going properly out of the network but can not read mac address.
Any advice would be wellcome.
Leandro.

Perhaps this line:

Serial.println("+++");

should be

Serial.print("+++");

If you wan to send "+++a" you don't want a newline after the "+++"