If you are using a usb to serial adapter you have to check to see which serial port the adapter is using(i.e. com 1 com 2, com 3....) Then you have to set the cutting software to use that port. The problem with USB to serial converters is that each time you remove and insert the adapter the serial port may increase. If it was set to com 2 and you removed and reinserted it the serial port may now site on Com 3. I had this problem with a laptop we use with Flexi. There are two ways to fix this. The first is to set the cutting sotware to use the port that the adapter is currenlty sitting on. The other is easy but has a few more stets. The 2nd method is: You have to go to the control panel, double click the system icon. That opens up the system properties, choose the hardware tab and then click on the Device Manager Button. In the device manager go down the list and expand the Ports(COM & LPT) sub list. Double clicke the adapter line and go to Port Setting and hit the advanced button. You can than move the port to whatever you want so it'll match the cutting software. Hope this helps