Can not communicate with Arduino Uno

Hi!

I have an two Arduino Uno R3's, one of them works perfectly, but the other does not.

When I plug the Arduino in nothing happens, and no COM port is available, also there is nothing in Device Manager.

I also tried programming it using an FTDI cable and plugging into the corresponding pins with no luck.

Any suggestions?

Is it a real Arduino?

If so, or the ATmega16u2 is broken or you need to burn the firmware again. See here.

I tried following the steps to burn the firmware again and I got this response form avrdude:

avrdude: Expected signature for ATmega16U2 is 1E 94 89

Possibile che sia usciti difetti ? Il mio venditore mi ha detto che vengono testati prima di essere messi in commercio

FrankyLeft:
Possibile che sia usciti difetti ? Il mio venditore mi ha detto che vengono testati prima di essere messi in commercio

It's not a new arduino, I got it from a friend but he had it laying around for awhile not sure if it got damaged.