I have 2 Arduino Uno's both were working fine connecting with mac usb ports until today. I tested my circuit with an external 9v power supply (no problems) but when I came back to plugging them into the usb ports I get serial port not found message, I have tried them on another computer and no luck either all i get are 6 bluetooth options.

Any idea's or will I have to get a new board?



Also forgot to add the power light still comes on just cant upload a sketch

Where did you get the Unos from?

Have you got any circuits connected to them?