Communication enter the roboteq's controller and PC using RS232

Hi !
I just start working with roboteq's technologies (FBL2360 controller) on my graduation's final project , and i try to send and recive commande from my PC using RS232 but it dosent work , i try with Rotorun plus , serial communication but it dosent work, it work with the usb and when i switched to serial port i lose connection