Here is the setup guide:
And since iOS is mentioned, make sure the device you use for the Google Home app has no VPN enabled/ connected; not any 3rd party product, nor the "Apple iCloud Private Relay" ( https://support.apple.com/en-us/HT212614 ).
Also make sure the Google Home app has been granted permission for "local network access" ( https://support.google.com/chromecast/answer/7172427?hl=en ).
I just wanted to jump in real fast to see if you saw olavrb's reply and to see if you still needed some help on this or if you were able to get it sorted out. If you are still needing some help, just let us know and we'll be happy to continue helping.
Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.