I am not familiar with the LPKF electronics. If it just a DB25 to break out to stepper driver modules? When you say it won't communicate do you mean the motors won't move or is there a "hand shake protocol" that has to be made to a micro controller in the machine? Feel free to post photos of the circuit boards.
When you turn it on, do you get stepper lockup so you know they are being energized? Are their any status LEDs?
The problem I am having is that the software to control the machine (boardmaster 5.0 - running on my computer) cannot connect to the machine over the serial port. When I turn the machine on, it zeros the x and y axis. So the steppers as well as the motor drivers are all working.