Same problem except I just received mine new this week.  Have my return label and will be sending it back.  Love Sonos when it works but this kind of BS is just not acceptable at this price point.  Hope you get yours to work.  I have zero confidence if I eventually was able to get it registered that it will work reliably.  Sonos software is awful.  

Thanks ! Will try the support tomorrow to see if there is anything they can suggest.  

I was finally able to get mine registered by using my wife’s phone. 

Let me try this ! Your wife is set up as a new user ? 

I have 2 new Fives and 2 new gen3 Subs.  After multiple repeated attempts and upgrades for all (why does Sonos SW do something different every time?!) I was able to get the Fives in stereo pair and one of the subs connected.  Tried to connect the second sub, it wanted to be updated.  Updated it.  Still couldn’t connect.

Called support.  I waited on the phone for 70 minutes, then spent 30 more minutes trying to get answers.  Eventually they said that you cannot connect 2 Fives in stereo pair with 2 subs.  “must be a home theater setup.”  Wha?!  It IS my home theater setup!  So I unplugged the first sub, tried to assign the second sub to the Fives.  “Check network connection.”  Factory reset.  Updated SW again.  Still won’t assign.  Went back to the first sub, now it won’t connect.

So after all the upgrades and thrashing around, I now have 2 subs that are basically big black bricks.  I agree, Sonos software sucks.  Maybe they should spend more $$ on engineering support rather than fancy marketing websites.  I submitted for a return label, will send ALL of it back.