cannot connect HomePod to the wifi used on my Iphone

Make sure that your setup device is not using private network address for your wi-fi network. See Use private Wi-Fi addresses on iPhone, iPad, iPod touch, and Apple Watch - Apple Support for details. Make sure the wi-fi router isn't in guest mode or otherwise blocking peer-to-peer traffic on your network.

tt2

I have just found that "Use Cellular Date" should be off. Once I turned that off, it connects again. Time will tell as I've thought I've fixed it before.