I'm in a jam, for the last week I've been trouble shooting my Fanuc om linking to my PC so, I finally got fed up and bought a rs232 tester to check the cable/connecters and its fine. The controller will send out accurately to my PC but It absolutely will not receive. The tester shows data making it to the serial port on the controller, but the "ZST" keeps flashing.. nothing shows up. Again, I can send to my PC, but I cant send to my CNC, so my questions are....

Can somebody tell me whats wrong, what do I do to fix it, and how much will it cost. What are my options? Any help is greatly appreciated.