Had you tried using it as a HID device previously?
It might be you've fallen foul of "I can't reconnect to my Puck.js on Mac OS" here: http://www.espruino.com/Puck.js#troubleshooting
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Had you tried using it as a HID device previously?
It might be you've fallen foul of "I can't reconnect to my Puck.js on Mac OS" here: http://www.espruino.com/Puck.js#troubleshooting