Trying to configure IFTTT and it Home Assistant pop-up message says server is not accessible from the internet

Trying to configure IFTTT and it Home Assistant pop-up message says server is not accessible from the internet.
I can access Home Assistant from the internet on https://hass.domain.com
I do happen to have a Traefik reverse proxy that handles forwarding ports and SSL cert.
Here is the entry which isn’t working

config:
https:
  base_url: hass.domain.com