HassIo + DuckDns + Google Assistant


I have troubles understanding what I am doing wrong…
I installed HassIo and the DuckDNS app.
I am able to connect to my homeassistant via http://xxxx.duckdns.org via the pc I did the configuration on.
All my other devices I am not able to connect as it gives an error “403 Forbidden”

now this offcourse gives extra troubles since I would like to install Google Assistant on my HassIo.
Since at one point you need to do some parts in the Google Home app, which is only available in the android or IOS store…

Please help!