Did you try a different USB cable or verify that the USB cable you're using works for data on a different device? You may have a damaged or charge-only cable.
Does it work without the Yun shield on the Uno?
Did you try a different USB cable or verify that the USB cable you're using works for data on a different device? You may have a damaged or charge-only cable.
Does it work without the Yun shield on the Uno?