Duckdns do not connect

Hello
I have just reinstalled hass.io on my raspberry with SSD, from scratch, and have installed the duckdns addon, and think I have configured everything as it should be. Forwarded port 8123 in my router. The duckdns log is ok, and nothing in the HA log. But when trying to access from outside I get the blue top banner and a blank page for a while, before I get the logo and “unable to connect to Home Assistant” and “retry”.
There is no problem connecting from within my network with the IP address.

Duckdns config:

{
  "lets_encrypt": {
    "accept_terms": true,
    "certfile": "fullchain.pem",
    "keyfile": "privkey.pem"
  },
  "token": "xxxxxxxx-c5f1-4f6f-830d-11ef4ab1fab7",
  "domains": [
    "mydomain.duckdns.org"
  ],
  "seconds": 300

Configuration.yaml

# Configure a default setup of Home Assistant (frontend, api, etc)
default_config:



# Text to speech
tts:
  - platform: google_translate

group: !include groups.yaml
automation: !include automations.yaml
script: !include scripts.yaml

# Example configuration.yaml entry
device_tracker:
  - platform: nmap_tracker
    hosts: 192.168.10.1/24
    
http:
  base_url: https://mydomain.duckdns.org
  ssl_certificate: /ssl/fullchain.pem
  ssl_key: /ssl/privkey.pem

Any ideas what’s wrong?