I'm using an arduino leonardo in Arduino IDE 1.6.4 on a mac osx 10.9.5. When I first plug in the arduino, the ide will recognize the leonardo on the correct port. I try to upload to the arduino using the port that says usbmodem621 (Arduino Leonardo) then within about 10 seconds, it stops recognizing the arduino and that port is no longer an option. Any idea what is happening or how I can fix this?
I have tried different usb cables and my Mega is recognized just fine in both USB ports I tried
Try uploading the blink sketch, and press the reset button on the Leonardo when you click upload.