Windows Fax and Scan does work on Network Device

Scanning device is an HP Photosmart All in One HP 2575. i first installed it as an USB device and Windows Fax and Scan recognized it and scanned nicely. I then installed it as a network device and WFS would not recognize it as a scanning device when I unplugged the USB cable. It prints just fine but will not scan. What might I have done wrong and how may I correct it? Thank you