Same issue for me but holding the on/off button for 12 seconds put it in programming mode but the Alexa app continued to say plug was unresponsive. I then used the app to delete the plug completely which removed it from the device list and from the group. I then reinstalled the device and it started working; then Alexa app said it was unresponsive; then it started working. It has been working for about 15 minutes so I will see.
The instructions on the Amazon web site should be improved to include these possible solutions.
I have a similar issue. My new Amazon plug will not register with the Alexa app. I have reset it several times and I can’t get it to connect to my Wi-Fi network. After several minutes, I get the (-1: -3: -1 :-1) error code. Is there anything I can do, or should I just send the plug back?