The WiFi Selection ScreenThere's a point where you see a screen a bit like this:
When I selected my WiFi, I expected it to indicate my selection - ether with a dot or tick to the left or biy highlighting the whole line. It didn't - which also surprised the Google support person I was chatting to. Maybe it's something about the colour set up on my phone? Anyway, here's the work around - don't worry about the lack of visual feedback, tap the correct item and then "Next". You'll see on the next page that it noted which entry you tapped and is now using it.
Your WiFi Setup
Not all WiFi is equal - which you probably knew already - but some of them are less equal than others. I set up my broadband router to offer a "guest" WiFi for visitors and was using that. This resulted in Google Home announcing that my smart speaker "was set up successfully but can't be found" which is pretty silly - how can you set up a device you can't find? So I fixed this by using the standard WiFi account (which seems to have more privileges) shown in red below and keep the "Guest Wi-Fi" strictly for guests.
|(Your router screen may vary)|