After installing my product driver my product is installed as an 'unknown device' in the device manager. Why?

• During plug-and-play installation, some problem disrupted the installation. While the printer is connected through the USB cable and the power is on, check the Device Manager in the My Computer menu. If USB printer or EPL-5700i is installed in unknown device, then the printer hasn't been properly installed. Disconnect the USB cable from the printer, then reconnect it and reinstall the printer driver.