Account Linking - Alexa not working

I run HASSIO with duckdns and encryption. I can access my home assistant with duckdns without problem.

I’ve been trying to link my Alexa by following the instruction here:
https://www.home-assistant.io/components/alexa.smart_home/

I follow the manual (not using home assistant cloud) procedure until the last step to enable link to home assistant from Alexa web. It always produces

I really don’t know how to solve this problem. Any suggestion would be really appreciated.

I recommend updating to the latest HA if you haven’t already.

However I can’t get it to work also, I’m getting this error:

We were unable to link Home Assistant at this time.
For instructions and assistance with configuring your skill for account linking with OAuth, please see this guide.

If you did get it working, please let me know what you changed to get it going!