Ok i checked you details against the manual located here www.lz4gv.com/CNC_files/3Axis_Driver_txt.pdf and it checks out correct so if all the wires are properly secured then it must be a problem on the board. I will assume you are using nema23 motors and the voltages for that motor are correct? they are wired for parallel operation?

Have you tried swapping the motors around to eliminate they are he problem? Check the bios on your pc and swap between ecp and epp if you can, some bios have these together or separate. If all this is ok the power up and switch on (not running any operation and check for voltage on the output pins of the board to the motors (A+). Which ever one is not working trace back to before the driver chip to the input pin and see if it is getting a supply. If not then the chance are it will just be one of the opto isolator IC's. You can confirm this by swapping it for one of the others. If they are ok then it will be one of the driver chips. I hope this gets you going in the right direction to sort it.

Paul