Try unplugging and replugging in the USB cable.Make sure you haven't connected an Android phone at the same time as the Firefox OS phone to your computer.This is a good idea because when the screen gets locked, the phone connection gets lost, meaning it is no longer available for debugging. Disable screen lock on your device: in the Settings app on the device, go to Screen Lock and unchecking the Lock Screen checkbox.Firefox OS 1.4 and later: 'Remote Debugging' asks you to enable for just ADB, or for ADB and DevTools.Firefox OS 1.3 and earlier: 'Remote Debugging' is just a simple checkbox.On previous versions, go to Dev ice information > More information > Developer.Enable remote debugging: in the Settings app on the device, go to Developer > Debugging via USB.If you don't have a high enough version, find your device in the developer phone guide and follow the instructions for upgrading.

To check the version, go to the Settings app on the device, then Device Information > Software. Check your Firefox OS version: make sure your device is running Firefox OS 1.2/Boot2Gecko 1.2 or later.If you're trying to connect a Firefox OS device to WebIDE and it doesn't show up, here are some things you can try:

Firefox os x troubleshooting