Do you already have the or are you using a third-party cable ?
This is the most common issue. It is almost always a driver issue. Check your Windows Device Manager to ensure the programming cable is recognized as a "USB Serial Port" or similar device. If there is a yellow exclamation mark, you may need to download generic USB-to-Serial drivers (often Prolific or FTDI drivers depending on the cable manufacturer). motorola evx-261 programming software