I bought a brand new Leo, and upon connecting it to the IDE, the PORT option was left greyed out. I tried to follow some fixes, but nothing came up in Device Manager. Strange thing is, my Uno works just fine, not my leo, what do I do?
Make sure the USB cable is completely plugged into both the Arduino board and the PC.
You may have a damaged/defective or charge-only USB cable. Try a different cable.