I have a Sonos Arc, Five, Sub (Gen 3), turntable. 
 

my sub will not register to my arc but I got it paired with my five so it all kinda worked out.

just got two ERA 300. They add to WiFi and Bluetooth just fine but will not register no matter what. 
 

I tried factory reset. 
 

I tried new dedicated network. 
 

I tried hardwire connection. 
 

I moved closer to the APs.

i removed every single other device on network and have nothing but era 300 connected. 
 

the product will not register.