Verify that the serial port for the USB cable connected to your KPA1500 is the one you have chosen on the Port page.
You may find it helpful to unplug the KPA1500 USB cable from your computer, click "Refresh Port List" on the Port page, examine the list of serial ports shown under the Serial Port drop down menu, then plug in the USB cable, click "Refresh Port List" again and look for the serial port that is added when the USB cable is plugged in.