Riva:
What pins is it wired to. From the manual
And your using pins 7, 8 & 10 on the edge connector, connected to pins 3, 2 & 5 on the 9 pin D connector? If yes and it does not work the try swapping pin 7 & 8 over. What RS232 TTL converter chip/board/shield are you using and how is it connected to the arduino. You won't be able to connect it to pins 0 & 1 on the arduino if your using USB & Serial to the PC so will need to use either a Mega and connect to one of the other serial ports or use SoftwareSerial.