I’ve had an incredibly frustrating couple of weeks with speakers suddenly dropping and not reconnecting after trying all troubleshooting and multiple customer service calls.

Here’s what I figured out with my Telus internet provider:

Admin settings were changed to turn off smartstream which has both 2.4 and 5G. Once two separate wifi networks were created for each band, my speakers connected and showed up using 2.4g only.. even though other things run without a problem on 5G in my home. Confirmed I have 4 Sonos ONE GEN 2 and ARC all of which should work on 5G. 
 

After I reconnected all my speakers for the first time without problems in weeks, I renamed the rooms and the system disappeared. This happened two times. I had to unplug all Sonos speakers, start a new system, factory reset and add each speaker one by one on the 2.4g only network. I didn’t rename them, and so far they’ve been connected since last night. 
 

Seems that there needs to be a fix for this.