NOTE: If you have used the device on another computer. You may need to do the following :

1. Connect to the new computer.
2. Go into developer settings.
3. Turn off USB or Wifi Debugging.
4. Turn on USB or Wifi Debugging again.

You will be prompted to accept debugging on the new Mac address. Accept this always.

I found when debugging on different machines, this can sometimes be a required step on certain phones.