if its showing communication error it means connections are not properly connected

Did you use the computer assaigned to it for other purpose as well? Especially, have you use the USB port for any other device (flash disk, ...)? I have had this problem as well, there was a problem with USB driver.

Try to install Voltamaster software to another PC and try it there.

Thanks Josef, i will try as what you have suggested.

Thanks Prof Mohd Hazwan