I'm having the same issue... read through all the help screens etc but
the Google Home app does not see this Chromecast or an older Nexus TV
devices on the same Wifi network etc.
I have the same issue - cannot add this Chromecast audio (2nd gen) or an
older Nexus TV to the Google Home app following all posted
instructions... Please Google/Nest/legacy team update these online help
screens for the new firmware, etc.
