Error linking Alexa account

Hi all, I’m newby in HASS.
I’m getting an error trying to linking Alexa with Home Assistant. I did follow the steps defined in : Amazon Alexa Smart Home Skill - Home Assistant

I have SSL DuckDNS … but published in port 9443 instead of 443.
I’m stuck trying to link my new skill with Alexa. I can login in my HASS but Alexa mobile app shows : “Not possible to link your account with Alexa”

This process is still working¿?

Thanks!