OK, factory reset of the Nest Mini V2 (per this thread:
https://www.googlenestcommunity.com/t5/Speakers-and-Displays/Nest-mini-and-audio-will-not-connect-to-wifi/m-p/69495)
solved it!
I'm having the same problem with my Nest Mini but Leslied's solution
(trying to set it up via an iPhone) hasn't worked for me. Google, can
you please help fix this?