Ipv6 - ipv4 map https proxy error 400 websocket

Hi,
I have ds-lite only public ipv6.
Earlier I tried to set it all up with (HASSIO) and additional Caddy 2, Nginx Proxy Manager (SSL), duckdns.
Unfortunately, two things did not work as I wanted…

  • there was no ipv4 access to hassio
  • Google assistant could not be integrated

I had another idea
ipv4 <-> ipv6 + proxy https port mapping
via the feste-ip.net website

Unfortunately, appeared the following problem

400 Bad Request websocket!
festeip|690x414

How to fix it?