First off, has it ever communicated? If yes, can't really help you unfortunately.
Are you using the RS232 port or the Lan port? (If setting Baud, must be RS232 I assume)
We had a horizontal with the 640 control and we could not communicate with it using RS232 port, but we could via the floppy drive.
Phoned the experts at Mazak, sent me a new Mobo to 25 pin cable assy, on attempting to fit it, found the original was not connected at the Mobo.
Turns out the same port is used on the Mobo for comms to and from the tool management control option.
Supposedly you can connect to the other port on the Mobo with this lead, but we didn't bother as they only wanted to use a Facit 1060, backwards step if the machine has a floppy.