Hello,
I am running out of options so i solicit some help 
I had a functional google assistant integration before moving from an ISP to another.
Shortly , i had a static IPv4 but not anymore so i tried to move my whole system into IPv6.
I have a Synology exposed behind a DNS and acting like a reverse proxy so my ipv6 firewall opens the 443 of the Syno which redirects the url to the hassio port.
Everything seems working smoothly except the google home / assistant integration.
I am blocked at the step where i have to add the new services in the google Home App:
I pass successfully the login page but then appears a generic error and i can’t find out where is the problem:
There is no log in the Google console and i can’t find anything either on the Home Assistant App.
I am trying to setup Google Assistant with the “Manual setup” documentation:
Url “…/api/google_assistant” can be reached externally
I see the Google action in the google home app, can login but right after it fails …
My configuration file :
Do you have any clue ?