Arduino Uno not appearing under ports I have an Arduino Uno attached to my MacBook Air running the Arduino IDE 1.6.4.

The Arduino was visible in the Serial port section this morning, but then it just disappeared. The ON light on the Arduino still comes on, but I cannot connect to it through the port section. I attached the Uno to another computer and it did not appear there either. However, when a different Arduino is connected to my computer it does show up. I also tried using a different IDE version, and it did not appear there either.

All of the other topics I found regarding this were saying it is the OS's fault, but since I was able to see the other Arduino, I am pretty sure it is not. I updated the FTDI drivers, and I tried using a powered hub and it is still not there.

UPDATE:

When I took the chip out of the UNO that is not appearing and put it into a working UNO, I was able to see it, is it possible that the Serial port is just not working, and if so how would I fix that

Any help would be appreciated.
If the Arduino doesn't show up on multiple computers, and others do, it may be bricked, or dead. You might try reflashing the chip, and hope that solves your issue. If it doesn't, chances are it's toast.

If however the device simply doesn't show up on one computer, but does on another. It's either a software issue, or a USB issue with that computer.

If winblows OS, try reinstalling, or updating the drivers for the USB, as well as the Arduino. And check your power management on the USB as well. I've seen Windows USB poop the bed if a device is connected / disconnected, or restarted several times in rapid succession. When this happens, sometimes Windows will think the port or device is faulty, and simply stop responding to its presence.

If *nix, make sure you've configured it properly.