I spent half of my day after purchasing the IKEA SYMFONISK gen 2 speakers failing at setup. 
 

I reset the speakers, router, phone, and unplugged each device numerous times. The devices appear and begin the setup process through wi-fi but eventually fail to connect. The router is 5 feet away from my sonos speakers.

Not even a direct ethernet wire would work for me.  I have not found a useful tip or video that troubleshoots this nightmare process.