When I try and authenticate using the URL that is shown in the log when I restarted homebridge, I get taken to an Amazon screen that says "Scan QR code with your phone’s camera to open the Alexa app." instead of the screen that asks for my credentials. I have installed this plugin as a child bridge, and followed the other instructions in the readme. The main difference I see is I get this message in the log:
Homebridge v1.6.1 (HAP v0.11.1) (homebridge-alexa-smarthome) is running on port 51405 instead of port 9000 which is what I set in the plugin settings.
Please let me know if I can provide any more information.