Answer: New security enhancements in android 4.2.2 builds (and above) require the end user to explicitly grant adb access to any connecting computers before that connecting machine can successfully issue any adb commands to your device. When you connect a 4.2.2 (and above) android device to your machine (with USB debugging enabled) for the first time, you should be prompted with a confirmation message to allow or disallow USB debugging. This message will display your computers unique RSA key fingerprint and provide you a checkbox to “Always allow from this computer”. Check this box and select ‘OK’. Your device should no longer be listed as ‘offline’.
If you don’t see this prompt then you should try the following:
- With your device connected via usb and the toolkit running, toggle USB debugging off/on in Settings > ‘Developer Options’ and see if the prompt comes up.
- Also try unplugging and re-plugging the usb connection.
- Use the toolkits ‘Advanced Utilities’ > Quick Tools > List Devices (ADB mode)’ to test for device connectivity.
If you successfully accept the RSA fingerprint prompt and your device still remains listed as offline then follow the additional suggestions in the toolkit prompt.