Fiscal printers not receiving commands

Question

I have a thermal printer(DATECS FP-700CRX)... and it only prints using commands.

I've used several printing drivers including Mike42/escpos-php drivers but still can't get anything out from the printer.

Even a simple Hello World text receipt is failing to be printed. anyone to help resolve the issue, even just printing a simple Hello World text.

I've tried several codes and the recent one is below, but nothing shows up.

Am using RS232 serial port:

use Mike42\Escpos\Printer;
use Mike42\Escpos\EscposImage;
use Mike42\Escpos\PrintConnectors\FilePrintConnector;

$connector = new FilePrintConnector("COM9");
$printer = new Printer($connector);
$printer -> text("Hello World\n");
$printer -> cut();
$printer -> close();```